diff --git a/mapped_file.cpp b/mapped_file.cpp
index 7c65dc3..d26e8ba 100644
--- a/mapped_file.cpp
+++ b/mapped_file.cpp
@@ -76,7 +76,7 @@
   if (base_ != nullptr) UnmapViewOfFile(base_);
   if (handle_ != nullptr) CloseHandle(handle_);
 #else
-  if (base_ != nullptr) munmap(base_, size_);
+  if (base_ != nullptr) munmap(base_, size_ + offset_);
 #endif
 
   base_ = nullptr;