diff --git a/src/public/tier0/memdbgon.h b/src/public/tier0/memdbgon.h
index 822202aa9f3..415f50691ad 100644
--- a/src/public/tier0/memdbgon.h
+++ b/src/public/tier0/memdbgon.h
@@ -88,7 +88,7 @@ inline void *MemAlloc_InlineCallocMemset( void *pMem, size_t nCount, size_t nEle
 }
 #endif
 
-#define calloc(c, s)		MemAlloc_InlineCallocMemset(malloc(c*s), c, s)
+#define calloc(c, s)		MemAlloc_InlineCallocMemset( malloc( (c) * (s) ), c, s )
 #define free(p)				g_pMemAlloc->Free( p )
 #define _msize(p)			g_pMemAlloc->GetSize( p )
 #define _expand(p, s)		_expand_NoLongerSupported(p, s)