diff --git a/lib/isc/include/isc/astack.h b/lib/isc/include/isc/astack.h
index e0ea66ca2b..cd068c61f6 100644
--- a/lib/isc/include/isc/astack.h
+++ b/lib/isc/include/isc/astack.h
@@ -9,6 +9,8 @@
  * information regarding copyright ownership.
  */
 
+#pragma once
+
 #include <inttypes.h>
 #include <isc/mem.h>
 #include <isc/types.h>
diff --git a/lib/isc/include/isc/hp.h b/lib/isc/include/isc/hp.h
index 3cd542bd02..678c5f8b28 100644
--- a/lib/isc/include/isc/hp.h
+++ b/lib/isc/include/isc/hp.h
@@ -43,6 +43,8 @@
  * THE POSSIBILITY OF SUCH DAMAGE.
  */
 
+#pragma once
+
 #include <isc/atomic.h>
 #include <isc/string.h>
 #include <isc/mem.h>
diff --git a/lib/isc/netmgr/netmgr-int.h b/lib/isc/netmgr/netmgr-int.h
index 36ebd3aaa1..b4191ff6ef 100644
--- a/lib/isc/netmgr/netmgr-int.h
+++ b/lib/isc/netmgr/netmgr-int.h
@@ -9,6 +9,8 @@
  * information regarding copyright ownership.
  */
 
+#pragma once
+
 #include <unistd.h>
 #include <uv.h>