diff --git a/bin/named/win32/ntservice.c b/bin/named/win32/ntservice.c
index 17bb50527a..b0dd641054 100644
--- a/bin/named/win32/ntservice.c
+++ b/bin/named/win32/ntservice.c
@@ -15,6 +15,7 @@
 #include <isc/commandline.h>
 #include <isc/log.h>
 #include <isc/print.h>
+#include <isc/string.h>
 
 #include <named/globals.h>
 #include <named/ntservice.h>
diff --git a/bin/tests/sock_test.c b/bin/tests/sock_test.c
index 0ade9e7444..64a518c4c6 100644
--- a/bin/tests/sock_test.c
+++ b/bin/tests/sock_test.c
@@ -16,8 +16,9 @@
 
 #include <isc/mem.h>
 #include <isc/print.h>
-#include <isc/task.h>
 #include <isc/socket.h>
+#include <isc/string.h>
+#include <isc/task.h>
 #include <isc/timer.h>
 #include <isc/util.h>
 
diff --git a/lib/isc/pk11.c b/lib/isc/pk11.c
index 00e8f48584..bfb9859591 100644
--- a/lib/isc/pk11.c
+++ b/lib/isc/pk11.c
@@ -18,6 +18,7 @@
 #include <isc/platform.h>
 #include <isc/print.h>
 #include <isc/stdio.h>
+#include <isc/string.h>
 #include <isc/thread.h>
 #include <isc/util.h>
 
diff --git a/lib/isc/win32/socket.c b/lib/isc/win32/socket.c
index fa752dc1b0..bbdc6c1303 100644
--- a/lib/isc/win32/socket.c
+++ b/lib/isc/win32/socket.c
@@ -59,6 +59,7 @@
 #include <isc/socket.h>
 #include <isc/stats.h>
 #include <isc/strerror.h>
+#include <isc/string.h>
 #include <isc/syslog.h>
 #include <isc/task.h>
 #include <isc/thread.h>