diff --git a/Makefile b/Makefile
index 10528f8..b70e7ec 100644
--- a/Makefile
+++ b/Makefile
@@ -46,7 +46,7 @@ endif
 
 # Disable runtime asserts
 ifeq ($(RUNTIME_ASSERT), false)
-	override BUILD_FLAGS += WAPP_NO_RUNTIME_ASSERT
+	override BUILD_FLAGS += -DWAPP_NO_RUNTIME_ASSERT
 endif
 
 ifeq ($(CC),gcc)