diff --git a/CMakeLists.txt b/CMakeLists.txt
index 6b52b48e..d43279ab 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,5 +1,5 @@
 cmake_minimum_required(VERSION 3.8)
-project(ccls LANGUAGES CXX)
+project(ccls LANGUAGES CXX C)
 
 option(USE_SYSTEM_RAPIDJSON "Use system RapidJSON instead of the git submodule if exists" ON)