diff --git a/Makefile b/Makefile
index 2f5c485f..5b07de3d 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-CLANG_FORMAT ?= clang-format-5.0
+CLANG_FORMAT ?= clang-format-3.9
 
 .PHONY: database format clean env