diff --git a/m-core.h b/m-core.h
index 42a2b436..3873fb2b 100644
--- a/m-core.h
+++ b/m-core.h
@@ -26,6 +26,7 @@
 #define __M_MACRO_H
 
 #include <stddef.h>
+#include <stdbool.h>
 #include <assert.h>
 
 /***************************************************************/