diff --git a/runtime/gc/collector/immune_spaces.cc b/runtime/gc/collector/immune_spaces.cc
index 1e5f283..26da4ca 100644
--- a/runtime/gc/collector/immune_spaces.cc
+++ b/runtime/gc/collector/immune_spaces.cc
@@ -16,9 +16,6 @@
 
 #include "immune_spaces.h"
 
-#include <vector>
-#include <tuple>
-
 #include "gc/space/space-inl.h"
 #include "mirror/object.h"
 #include "oat_file.h"
@@ -35,12 +32,11 @@
 void ImmuneSpaces::CreateLargestImmuneRegion() {
   uintptr_t best_begin = 0u;
   uintptr_t best_end = 0u;
-  uintptr_t best_heap_size = 0u;
   uintptr_t cur_begin = 0u;
   uintptr_t cur_end = 0u;
-  uintptr_t cur_heap_size = 0u;
-  using Interval = std::tuple</*start*/uintptr_t, /*end*/uintptr_t, /*is_heap*/bool>;
-  std::vector<Interval> intervals;
+  // TODO: If the last space is an image space, we may include its oat file in the immune region.
+  // This could potentially hide heap corruption bugs if there is invalid pointers that point into
+  // the boot oat code
   for (space::ContinuousSpace* space : GetSpaces()) {
     uintptr_t space_begin = reinterpret_cast<uintptr_t>(space->Begin());
     uintptr_t space_end = reinterpret_cast<uintptr_t>(space->Limit());
@@ -54,47 +50,29 @@
       // creation, the actual oat file could be somewhere else.
       const OatFile* const image_oat_file = image_space->GetOatFile();
       if (image_oat_file != nullptr) {
-        intervals.push_back(Interval(reinterpret_cast<uintptr_t>(image_oat_file->Begin()),
-                                     reinterpret_cast<uintptr_t>(image_oat_file->End()),
-                                     /*image*/false));
+        uintptr_t oat_begin = reinterpret_cast<uintptr_t>(image_oat_file->Begin());
+        uintptr_t oat_end = reinterpret_cast<uintptr_t>(image_oat_file->End());
+        if (space_end == oat_begin) {
+          DCHECK_GE(oat_end, oat_begin);
+          space_end = oat_end;
+        }
       }
     }
-    intervals.push_back(Interval(space_begin, space_end, /*is_heap*/true));
-  }
-  std::sort(intervals.begin(), intervals.end());
-  // Intervals are already sorted by begin, if a new interval begins at the end of the current
-  // region then we append, otherwise we restart the current interval. To prevent starting an
-  // interval on an oat file, ignore oat files that are not extending an existing interval.
-  // If the total number of image bytes in the current interval is larger than the current best
-  // one, then we set the best one to be the current one.
-  for (const Interval& interval : intervals) {
-    const uintptr_t begin = std::get<0>(interval);
-    const uintptr_t end = std::get<1>(interval);
-    const bool is_heap = std::get<2>(interval);
-    VLOG(collector) << "Interval " << reinterpret_cast<const void*>(begin) << "-"
-                    << reinterpret_cast<const void*>(end) << " is_heap=" << is_heap;
-    DCHECK_GE(end, begin);
-    DCHECK_GE(begin, cur_end);
-    // New interval is not at the end of the current one, start a new interval if we are a heap
-    // interval. Otherwise continue since we never start a new region with non image intervals.
-    if (begin != cur_end) {
-      if (!is_heap) {
-        continue;
-      }
-      // Not extending, reset the region.
-      cur_begin = begin;
-      cur_heap_size = 0;
+    if (cur_begin == 0u) {
+      cur_begin = space_begin;
+      cur_end = space_end;
+    } else if (cur_end == space_begin) {
+      // Extend current region.
+      cur_end = space_end;
+    } else {
+      // Reset.
+      cur_begin = 0;
+      cur_end = 0;
     }
-    cur_end = end;
-    if (is_heap) {
-      // Only update if the total number of image bytes is greater than the current best one.
-      // We don't want to count the oat file bytes since these contain no java objects.
-      cur_heap_size += end - begin;
-      if (cur_heap_size > best_heap_size) {
-        best_begin = cur_begin;
-        best_end = cur_end;
-        best_heap_size = cur_heap_size;
-      }
+    if (cur_end - cur_begin > best_end - best_begin) {
+      // Improvement, update the best range.
+      best_begin = cur_begin;
+      best_end = cur_end;
     }
   }
   largest_immune_region_.SetBegin(reinterpret_cast<mirror::Object*>(best_begin));
diff --git a/runtime/gc/collector/immune_spaces_test.cc b/runtime/gc/collector/immune_spaces_test.cc
index 75de6e6..56838f5 100644
--- a/runtime/gc/collector/immune_spaces_test.cc
+++ b/runtime/gc/collector/immune_spaces_test.cc
@@ -28,136 +28,7 @@
 namespace gc {
 namespace collector {
 
-class DummyOatFile : public OatFile {
- public:
-  DummyOatFile(uint8_t* begin, uint8_t* end) : OatFile("Location", /*is_executable*/ false) {
-    begin_ = begin;
-    end_ = end;
-  }
-};
-
-class DummyImageSpace : public space::ImageSpace {
- public:
-  DummyImageSpace(MemMap* map,
-                  accounting::ContinuousSpaceBitmap* live_bitmap,
-                  std::unique_ptr<DummyOatFile>&& oat_file,
-                  std::unique_ptr<MemMap>&& oat_map)
-      : ImageSpace("DummyImageSpace",
-                   /*image_location*/"",
-                   map,
-                   live_bitmap,
-                   map->End()),
-        oat_map_(std::move(oat_map)) {
-    oat_file_ = std::move(oat_file);
-    oat_file_non_owned_ = oat_file_.get();
-  }
-
- private:
-  std::unique_ptr<MemMap> oat_map_;
-};
-
-class ImmuneSpacesTest : public CommonRuntimeTest {
-  static constexpr size_t kMaxBitmaps = 10;
-
- public:
-  ImmuneSpacesTest() {}
-
-  void ReserveBitmaps() {
-    // Create a bunch of dummy bitmaps since these are required to create image spaces. The bitmaps
-    // do not need to cover the image spaces though.
-    for (size_t i = 0; i < kMaxBitmaps; ++i) {
-      std::unique_ptr<accounting::ContinuousSpaceBitmap> bitmap(
-          accounting::ContinuousSpaceBitmap::Create("bitmap",
-                                                    reinterpret_cast<uint8_t*>(kPageSize),
-                                                    kPageSize));
-      CHECK(bitmap != nullptr);
-      live_bitmaps_.push_back(std::move(bitmap));
-    }
-  }
-
-  // Create an image space, the oat file is optional.
-  DummyImageSpace* CreateImageSpace(uint8_t* image_begin,
-                                    size_t image_size,
-                                    uint8_t* oat_begin,
-                                    size_t oat_size) {
-    std::string error_str;
-    std::unique_ptr<MemMap> map(MemMap::MapAnonymous("DummyImageSpace",
-                                                     image_begin,
-                                                     image_size,
-                                                     PROT_READ | PROT_WRITE,
-                                                     /*low_4gb*/true,
-                                                     /*reuse*/false,
-                                                     &error_str));
-    if (map == nullptr) {
-      LOG(ERROR) << error_str;
-      return nullptr;
-    }
-    CHECK(!live_bitmaps_.empty());
-    std::unique_ptr<accounting::ContinuousSpaceBitmap> live_bitmap(std::move(live_bitmaps_.back()));
-    live_bitmaps_.pop_back();
-    std::unique_ptr<MemMap> oat_map(MemMap::MapAnonymous("OatMap",
-                                                         oat_begin,
-                                                         oat_size,
-                                                         PROT_READ | PROT_WRITE,
-                                                         /*low_4gb*/true,
-                                                         /*reuse*/false,
-                                                         &error_str));
-    if (oat_map == nullptr) {
-      LOG(ERROR) << error_str;
-      return nullptr;
-    }
-    std::unique_ptr<DummyOatFile> oat_file(new DummyOatFile(oat_map->Begin(), oat_map->End()));
-    // Create image header.
-    ImageSection sections[ImageHeader::kSectionCount];
-    new (map->Begin()) ImageHeader(
-        /*image_begin*/PointerToLowMemUInt32(map->Begin()),
-        /*image_size*/map->Size(),
-        sections,
-        /*image_roots*/PointerToLowMemUInt32(map->Begin()) + 1,
-        /*oat_checksum*/0u,
-        // The oat file data in the header is always right after the image space.
-        /*oat_file_begin*/PointerToLowMemUInt32(oat_begin),
-        /*oat_data_begin*/PointerToLowMemUInt32(oat_begin),
-        /*oat_data_end*/PointerToLowMemUInt32(oat_begin + oat_size),
-        /*oat_file_end*/PointerToLowMemUInt32(oat_begin + oat_size),
-        /*boot_image_begin*/0u,
-        /*boot_image_size*/0u,
-        /*boot_oat_begin*/0u,
-        /*boot_oat_size*/0u,
-        /*pointer_size*/sizeof(void*),
-        /*compile_pic*/false,
-        /*is_pic*/false,
-        ImageHeader::kStorageModeUncompressed,
-        /*storage_size*/0u);
-    return new DummyImageSpace(map.release(),
-                               live_bitmap.release(),
-                               std::move(oat_file),
-                               std::move(oat_map));
-  }
-
-  // Does not reserve the memory, the caller needs to be sure no other threads will map at the
-  // returned address.
-  static uint8_t* GetContinuousMemoryRegion(size_t size) {
-    std::string error_str;
-    std::unique_ptr<MemMap> map(MemMap::MapAnonymous("reserve",
-                                                     nullptr,
-                                                     size,
-                                                     PROT_READ | PROT_WRITE,
-                                                     /*low_4gb*/true,
-                                                     /*reuse*/false,
-                                                     &error_str));
-    if (map == nullptr) {
-      LOG(ERROR) << "Failed to allocate memory region " << error_str;
-      return nullptr;
-    }
-    return map->Begin();
-  }
-
- private:
-  // Bitmap pool for pre-allocated dummy bitmaps. We need to pre-allocate them since we don't want
-  // them to randomly get placed somewhere where we want an image space.
-  std::vector<std::unique_ptr<accounting::ContinuousSpaceBitmap>> live_bitmaps_;
-};
+class ImmuneSpacesTest : public CommonRuntimeTest {};
 
 class DummySpace : public space::ContinuousSpace {
  public:
@@ -201,41 +72,94 @@
   EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()), b.Limit());
 }
 
-// Tests [image][oat][space] producing a single large immune region.
+class DummyOatFile : public OatFile {
+ public:
+  DummyOatFile(uint8_t* begin, uint8_t* end) : OatFile("Location", /*is_executable*/ false) {
+    begin_ = begin;
+    end_ = end;
+  }
+};
+
+class DummyImageSpace : public space::ImageSpace {
+ public:
+  DummyImageSpace(MemMap* map,
+                  accounting::ContinuousSpaceBitmap* live_bitmap,
+                  std::unique_ptr<DummyOatFile>&& oat_file)
+      : ImageSpace("DummyImageSpace",
+                   /*image_location*/"",
+                   map,
+                   live_bitmap,
+                   map->End()) {
+    oat_file_ = std::move(oat_file);
+    oat_file_non_owned_ = oat_file_.get();
+  }
+
+  // Size is the size of the image space, oat offset is where the oat file is located
+  // after the end of image space. oat_size is the size of the oat file.
+  static DummyImageSpace* Create(size_t size, size_t oat_offset, size_t oat_size) {
+    std::string error_str;
+    std::unique_ptr<MemMap> map(MemMap::MapAnonymous("DummyImageSpace",
+                                                     nullptr,
+                                                     size,
+                                                     PROT_READ | PROT_WRITE,
+                                                     /*low_4gb*/true,
+                                                     /*reuse*/false,
+                                                     &error_str));
+    if (map == nullptr) {
+      LOG(ERROR) << error_str;
+      return nullptr;
+    }
+    std::unique_ptr<accounting::ContinuousSpaceBitmap> live_bitmap(
+        accounting::ContinuousSpaceBitmap::Create("bitmap", map->Begin(), map->Size()));
+    if (live_bitmap == nullptr) {
+      return nullptr;
+    }
+    // The actual mapped oat file may not be directly after the image for the app image case.
+    std::unique_ptr<DummyOatFile> oat_file(new DummyOatFile(map->End() + oat_offset,
+                                                            map->End() + oat_offset + oat_size));
+    // Create image header.
+    ImageSection sections[ImageHeader::kSectionCount];
+    new (map->Begin()) ImageHeader(
+        /*image_begin*/PointerToLowMemUInt32(map->Begin()),
+        /*image_size*/map->Size(),
+        sections,
+        /*image_roots*/PointerToLowMemUInt32(map->Begin()) + 1,
+        /*oat_checksum*/0u,
+        // The oat file data in the header is always right after the image space.
+        /*oat_file_begin*/PointerToLowMemUInt32(map->End()),
+        /*oat_data_begin*/PointerToLowMemUInt32(map->End()),
+        /*oat_data_end*/PointerToLowMemUInt32(map->End() + oat_size),
+        /*oat_file_end*/PointerToLowMemUInt32(map->End() + oat_size),
+        /*boot_image_begin*/0u,
+        /*boot_image_size*/0u,
+        /*boot_oat_begin*/0u,
+        /*boot_oat_size*/0u,
+        /*pointer_size*/sizeof(void*),
+        /*compile_pic*/false,
+        /*is_pic*/false,
+        ImageHeader::kStorageModeUncompressed,
+        /*storage_size*/0u);
+    return new DummyImageSpace(map.release(), live_bitmap.release(), std::move(oat_file));
+  }
+};
+
 TEST_F(ImmuneSpacesTest, AppendAfterImage) {
-  ReserveBitmaps();
   ImmuneSpaces spaces;
-  constexpr size_t kImageSize = 123 * kPageSize;
-  constexpr size_t kImageOatSize = 321 * kPageSize;
-  constexpr size_t kOtherSpaceSize= 100 * kPageSize;
-
-  uint8_t* memory = GetContinuousMemoryRegion(kImageSize + kImageOatSize + kOtherSpaceSize);
-
-  std::unique_ptr<DummyImageSpace> image_space(CreateImageSpace(memory,
-                                                                kImageSize,
-                                                                memory + kImageSize,
-                                                                kImageOatSize));
+  constexpr size_t image_size = 123 * kPageSize;
+  constexpr size_t image_oat_size = 321 * kPageSize;
+  std::unique_ptr<DummyImageSpace> image_space(DummyImageSpace::Create(image_size,
+                                                                       0,
+                                                                       image_oat_size));
   ASSERT_TRUE(image_space != nullptr);
   const ImageHeader& image_header = image_space->GetImageHeader();
-  DummySpace space(image_header.GetOatFileEnd(), image_header.GetOatFileEnd() + kOtherSpaceSize);
-
-  EXPECT_EQ(image_header.GetImageSize(), kImageSize);
+  EXPECT_EQ(image_header.GetImageSize(), image_size);
   EXPECT_EQ(static_cast<size_t>(image_header.GetOatFileEnd() - image_header.GetOatFileBegin()),
-            kImageOatSize);
-  EXPECT_EQ(image_space->GetOatFile()->Size(), kImageOatSize);
-  // Check that we do not include the oat if there is no space after.
-  {
-    WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    spaces.AddSpace(image_space.get());
-  }
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().Begin()),
-            image_space->Begin());
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()),
-            image_space->Limit());
-  // Add another space and ensure it gets appended.
+            image_oat_size);
+  DummySpace space(image_header.GetOatFileEnd(), image_header.GetOatFileEnd() + 813 * kPageSize);
   EXPECT_NE(image_space->Limit(), space.Begin());
   {
     WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
+    spaces.AddSpace(image_space.get());
     spaces.AddSpace(&space);
   }
   EXPECT_TRUE(spaces.ContainsSpace(image_space.get()));
@@ -246,109 +170,18 @@
   EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().Begin()),
             image_space->Begin());
   EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()), space.Limit());
-}
-
-// Test [image1][image2][image1 oat][image2 oat][image3] producing a single large immune region.
-TEST_F(ImmuneSpacesTest, MultiImage) {
-  ReserveBitmaps();
-  // Image 2 needs to be smaller or else it may be chosen for immune region.
-  constexpr size_t kImage1Size = kPageSize * 17;
-  constexpr size_t kImage2Size = kPageSize * 13;
-  constexpr size_t kImage3Size = kPageSize * 3;
-  constexpr size_t kImage1OatSize = kPageSize * 5;
-  constexpr size_t kImage2OatSize = kPageSize * 8;
-  constexpr size_t kImage3OatSize = kPageSize;
-  constexpr size_t kImageBytes = kImage1Size + kImage2Size + kImage3Size;
-  constexpr size_t kMemorySize = kImageBytes + kImage1OatSize + kImage2OatSize + kImage3OatSize;
-  uint8_t* memory = GetContinuousMemoryRegion(kMemorySize);
-  uint8_t* space1_begin = memory;
-  memory += kImage1Size;
-  uint8_t* space2_begin = memory;
-  memory += kImage2Size;
-  uint8_t* space1_oat_begin = memory;
-  memory += kImage1OatSize;
-  uint8_t* space2_oat_begin = memory;
-  memory += kImage2OatSize;
-  uint8_t* space3_begin = memory;
-
-  std::unique_ptr<DummyImageSpace> space1(CreateImageSpace(space1_begin,
-                                                           kImage1Size,
-                                                           space1_oat_begin,
-                                                           kImage1OatSize));
-  ASSERT_TRUE(space1 != nullptr);
-
-
-  std::unique_ptr<DummyImageSpace> space2(CreateImageSpace(space2_begin,
-                                                           kImage2Size,
-                                                           space2_oat_begin,
-                                                           kImage2OatSize));
-  ASSERT_TRUE(space2 != nullptr);
-
-  // Finally put a 3rd image space.
-  std::unique_ptr<DummyImageSpace> space3(CreateImageSpace(space3_begin,
-                                                           kImage3Size,
-                                                           space3_begin + kImage3Size,
-                                                           kImage3OatSize));
-  ASSERT_TRUE(space3 != nullptr);
-
-  // Check that we do not include the oat if there is no space after.
-  ImmuneSpaces spaces;
+  // Check that appending with a gap between the map does not include the oat file.
+  image_space.reset(DummyImageSpace::Create(image_size, kPageSize, image_oat_size));
+  spaces.Reset();
   {
     WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    LOG(INFO) << "Adding space1 " << reinterpret_cast<const void*>(space1->Begin());
-    spaces.AddSpace(space1.get());
-    LOG(INFO) << "Adding space2 " << reinterpret_cast<const void*>(space2->Begin());
-    spaces.AddSpace(space2.get());
-  }
-  // There are no more heap bytes, the immune region should only be the first 2 image spaces and
-  // should exclude the image oat files.
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().Begin()),
-            space1->Begin());
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()),
-            space2->Limit());
-
-  // Add another space after the oat files, now it should contain the entire memory region.
-  {
-    WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    LOG(INFO) << "Adding space3 " << reinterpret_cast<const void*>(space3->Begin());
-    spaces.AddSpace(space3.get());
+    spaces.AddSpace(image_space.get());
   }
   EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().Begin()),
-            space1->Begin());
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()),
-            space3->Limit());
-
-  // Add a smaller non-adjacent space and ensure it is not part of the immune region.
-  uint8_t* memory2 = GetContinuousMemoryRegion(kImageBytes + kPageSize);
-  std::unique_ptr<DummyImageSpace> space4(CreateImageSpace(memory2 + kPageSize,
-                                                           kImageBytes - kPageSize,
-                                                           memory2 + kImageBytes,
-                                                           kPageSize));
-  ASSERT_TRUE(space4 != nullptr);
-  {
-    WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    LOG(INFO) << "Adding space4 " << reinterpret_cast<const void*>(space4->Begin());
-    spaces.AddSpace(space4.get());
-  }
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().Begin()),
-            space1->Begin());
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()),
-            space3->Limit());
-
-  // Add a larger non-adjacent space and ensure it becomes the new largest immune region.
-  uint8_t* memory3 = GetContinuousMemoryRegion(kImageBytes + kPageSize * 3);
-  std::unique_ptr<DummyImageSpace> space5(CreateImageSpace(memory3 + kPageSize,
-                                                           kImageBytes + kPageSize,
-                                                           memory3 + kImageBytes + 2 * kPageSize,
-                                                           kPageSize));
-  ASSERT_TRUE(space5 != nullptr);
-  {
-    WriterMutexLock mu(Thread::Current(), *Locks::heap_bitmap_lock_);
-    LOG(INFO) << "Adding space5 " << reinterpret_cast<const void*>(space5->Begin());
-    spaces.AddSpace(space5.get());
-  }
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().Begin()), space5->Begin());
-  EXPECT_EQ(reinterpret_cast<uint8_t*>(spaces.GetLargestImmuneRegion().End()), space5->Limit());
+            image_space->Begin());
+  // Size should be equal, we should not add the oat file since it is not adjacent to the image
+  // space.
+  EXPECT_EQ(spaces.GetLargestImmuneRegion().Size(), image_size);
 }
 
 }  // namespace collector