diff --git a/lib/isc/tests/task_test.c b/lib/isc/tests/task_test.c
index 9cbe1c99c6..f4a44a12c5 100644
--- a/lib/isc/tests/task_test.c
+++ b/lib/isc/tests/task_test.c
@@ -23,6 +23,8 @@
 
 #define UNIT_TESTING
 
+#include <cmocka.h>
+
 #include <isc/atomic.h>
 #include <isc/cmocka.h>
 #include <isc/commandline.h>