diff --git a/include/wine/heap.h b/include/wine/heap.h
index 97d3a5662be..fb687c92393 100644
--- a/include/wine/heap.h
+++ b/include/wine/heap.h
@@ -46,7 +46,7 @@ static inline void heap_free(void *mem)
     HeapFree(GetProcessHeap(), 0, mem);
 }
 
-static inline void *heap_calloc(SIZE_T count, SIZE_T size)
+static inline void * __WINE_ALLOC_SIZE(1,2) heap_calloc(SIZE_T count, SIZE_T size)
 {
     SIZE_T len = count * size;
 
diff --git a/include/winnt.h b/include/winnt.h
index e853ddbc7ae..79df4259f59 100644
--- a/include/winnt.h
+++ b/include/winnt.h
@@ -199,9 +199,9 @@ extern "C" {
 #endif
 
 #if defined(__GNUC__) && ((__GNUC__ > 4) || ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 3)))
-#define __WINE_ALLOC_SIZE(x) __attribute__((__alloc_size__(x)))
+#define __WINE_ALLOC_SIZE(...) __attribute__((__alloc_size__(__VA_ARGS__)))
 #else
-#define __WINE_ALLOC_SIZE(x)
+#define __WINE_ALLOC_SIZE(...)
 #endif
 
 /* Anonymous union/struct handling */