diff --git a/ce/interp.h b/ce/interp.h
index a05881a..cf4500f 100644
--- a/ce/interp.h
+++ b/ce/interp.h
@@ -3,6 +3,7 @@
 
 #include "context.h"
 #include "parser.h"
+#include <stdbool.h>
 
 void execute (struct ast_node* root, struct context* context);