diff --git a/mrbgems/mruby-bigint/README-fgmp.md b/mrbgems/mruby-bigint/README-fgmp.md
index 3e5400dd5..24e131ba9 100644
--- a/mrbgems/mruby-bigint/README-fgmp.md
+++ b/mrbgems/mruby-bigint/README-fgmp.md
@@ -10,7 +10,7 @@ with the same API.
 For instance, you can link the following trivial program with either
 this code, or libgmp.a and get the same results.
 
-``` C
+```c
 #include <stdio.h>
 #include "gmp.h"
 main()