diff --git a/src/apps/cortex/support/observe.h b/src/apps/cortex/support/observe.h
index 63f6b39bed..032c3fcea2 100644
--- a/src/apps/cortex/support/observe.h
+++ b/src/apps/cortex/support/observe.h
@@ -10,6 +10,7 @@
 
 #include <Messenger.h>
 #include <Debug.h>
+#include <string.h>
 
 #include "cortex_defs.h"
 __BEGIN_CORTEX_NAMESPACE