diff --git a/src/snmalloc/override/malloc.cc b/src/snmalloc/override/malloc.cc
index fd5eca1..22d7824 100644
--- a/src/snmalloc/override/malloc.cc
+++ b/src/snmalloc/override/malloc.cc
@@ -41,6 +41,14 @@ extern "C"
     return snmalloc::libc::malloc_usable_size(ptr);
   }
 
+#ifdef _WIN32
+  SNMALLOC_EXPORT
+  size_t SNMALLOC_NAME_MANGLE(_msize)(MALLOC_USABLE_SIZE_QUALIFIER void* ptr)
+  {
+    return snmalloc::libc::malloc_usable_size(ptr);
+  }
+#endif
+
   SNMALLOC_EXPORT
   size_t SNMALLOC_NAME_MANGLE(malloc_good_size)(size_t size)
   {