diff --git a/include/leak_detector.h b/include/leak_detector.h
index f8161b27e..c85502c44 100644
--- a/include/leak_detector.h
+++ b/include/leak_detector.h
@@ -57,6 +57,9 @@
 #undef posix_memalign
 #define posix_memalign(p,a,n) GC_posix_memalign(p,a,n)
 
+#undef malloc_usable_size
+#define malloc_usable_size(p) GC_size(p)
+
 #ifndef CHECK_LEAKS
 # define CHECK_LEAKS() GC_gcollect()
   /* Note 1: CHECK_LEAKS does not have GC prefix (preserved for */
diff --git a/tests/leak_test.c b/tests/leak_test.c
index 37fa26b3f..f13d08138 100644
--- a/tests/leak_test.c
+++ b/tests/leak_test.c
@@ -23,6 +23,7 @@ int main(void) {
     for (i = 0; i < 10; ++i) {
         p[i] = (char*)malloc(sizeof(int)+i);
         CHECK_OUT_OF_MEMORY(p[i]);
+        (void)malloc_usable_size(p[i]);
     }
     CHECK_LEAKS();
     for (i = 1; i < 10; ++i) {