diff --git a/ext/fiddle/conversions.c b/ext/fiddle/conversions.c
index b0dcf84873..66058d5d12 100644
--- a/ext/fiddle/conversions.c
+++ b/ext/fiddle/conversions.c
@@ -1,3 +1,5 @@
+#include <stdbool.h>
+
 #include <fiddle.h>
 
 VALUE