diff --git a/lib/isc/win32/time.c b/lib/isc/win32/time.c
index fe41d85cf0..7f21e287b5 100644
--- a/lib/isc/win32/time.c
+++ b/lib/isc/win32/time.c
@@ -20,6 +20,7 @@
 #include <windows.h>
 
 #include <isc/assertions.h>
+#include <isc/string.h>
 #include <isc/time.h>
 #include <isc/tm.h>
 #include <isc/util.h>