diff --git a/core/main.mk b/core/main.mk
index 6baf6c4..f860f54 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -92,7 +92,7 @@
 # and host information.
 include $(BUILD_SYSTEM)/config.mk
 
-ifeq ($(USE_NINJA),true)
+ifneq ($(USE_NINJA),false)
 # Mark this is a ninja build.
 $(shell mkdir -p $(OUT_DIR) && touch $(OUT_DIR)/ninja_build)
 include build/core/ninja.mk