diff --git a/lib/isc/unix/socket.c b/lib/isc/unix/socket.c
index d1ac96f535..7d7e89cb52 100644
--- a/lib/isc/unix/socket.c
+++ b/lib/isc/unix/socket.c
@@ -34,6 +34,9 @@
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
+#ifdef HAVE_INTTYPES_H
+#include <inttypes.h> /* uintptr_t */
+#endif
 
 #include <isc/buffer.h>
 #include <isc/bufferlist.h>