diff --git a/osi/src/allocator.cc b/osi/src/allocator.cc
index 1c0449e..e2c356d 100644
--- a/osi/src/allocator.cc
+++ b/osi/src/allocator.cc
@@ -56,6 +56,7 @@
 }
 
 void* osi_malloc(size_t size) {
+  CHECK(static_cast<ssize_t>(size) >= 0);
   size_t real_size = allocation_tracker_resize_for_canary(size);
   void* ptr = malloc(real_size);
   CHECK(ptr);
@@ -63,6 +64,7 @@
 }
 
 void* osi_calloc(size_t size) {
+  CHECK(static_cast<ssize_t>(size) >= 0);
   size_t real_size = allocation_tracker_resize_for_canary(size);
   void* ptr = calloc(1, real_size);
   CHECK(ptr);