diff --git a/cc/makevars.go b/cc/makevars.go
index a71f479..78a32c8 100644
--- a/cc/makevars.go
+++ b/cc/makevars.go
@@ -161,6 +161,8 @@
 
 	ctx.Strict("AIDL_CPP", "${aidlCmd}")
 
+	ctx.Strict("M4", "${m4Cmd}")
+
 	ctx.Strict("RS_GLOBAL_INCLUDES", "${config.RsGlobalIncludes}")
 
 	ctx.Strict("SOONG_STRIP_PATH", "${stripPath}")