diff --git a/core/main.mk b/core/main.mk
index 4578d90..37b2367 100644
--- a/core/main.mk
+++ b/core/main.mk
@@ -33,6 +33,8 @@
 
 include $(SOONG_MAKEVARS_MK)
 
+YACC :=$= $(BISON) -d
+
 include $(BUILD_SYSTEM)/clang/config.mk
 
 # Write the build number to a file so it can be read back in