diff --git a/reactos/rules.mak b/reactos/rules.mak
index af95a068578..9dd26529c47 100644
--- a/reactos/rules.mak
+++ b/reactos/rules.mak
@@ -60,7 +60,7 @@ else
 DEBUGGING_CFLAGS = 
 endif
 
-DEFINES = -DDBG
+DEFINES = -DDBG -DCHECKED
 
 ifeq ($(WIN32_LEAN_AND_MEAN),yes)
 LEAN_AND_MEAN_DEFINE = -DWIN32_LEAN_AND_MEAN