diff --git a/oldXMenu/ChgPane.c b/oldXMenu/ChgPane.c
index d2977b73faf..733f65950f5 100644
--- a/oldXMenu/ChgPane.c
+++ b/oldXMenu/ChgPane.c
@@ -14,6 +14,7 @@
  */
 
 #include "XMenuInt.h"
+#include <string.h>
 
 int
 XMenuChangePane(register XMenu *menu, register int p_num, char *label)
diff --git a/oldXMenu/ChgSel.c b/oldXMenu/ChgSel.c
index d24e61f56d5..5a46b5cf587 100644
--- a/oldXMenu/ChgSel.c
+++ b/oldXMenu/ChgSel.c
@@ -14,6 +14,7 @@
  */
 
 #include "XMenuInt.h"
+#include <string.h>
 
 int
 XMenuChangeSelection(Display *display, register XMenu *menu, register int p_num, register int s_num, char *data, int data_sw, char *label, int label_sw)
diff --git a/oldXMenu/Create.c b/oldXMenu/Create.c
index 0e72a2d2e58..a0913685365 100644
--- a/oldXMenu/Create.c
+++ b/oldXMenu/Create.c
@@ -31,6 +31,7 @@ along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "XMenuInt.h"
 #include <stdlib.h>
+#include <string.h>
 
 #ifdef EMACS_BITMAP_FILES
 #include "../src/bitmaps/dimple1.xbm"
diff --git a/oldXMenu/InsPane.c b/oldXMenu/InsPane.c
index d8470f3a5bf..da92f49aa77 100644
--- a/oldXMenu/InsPane.c
+++ b/oldXMenu/InsPane.c
@@ -15,6 +15,7 @@
  */
 
 #include "XMenuInt.h"
+#include <string.h>
 
 int
 XMenuInsertPane(register XMenu *menu, register int p_num, char *label, int active)
diff --git a/oldXMenu/InsSel.c b/oldXMenu/InsSel.c
index 66f4968197d..f5380437958 100644
--- a/oldXMenu/InsSel.c
+++ b/oldXMenu/InsSel.c
@@ -14,6 +14,7 @@
  */
 
 #include "XMenuInt.h"
+#include <string.h>
 
 int
 XMenuInsertSelection(register XMenu *menu, register int p_num, register int s_num, char *data, char *label, int active)