diff --git a/xgraph/idraw.c b/xgraph/idraw.c
index c411c58c1..620263b8d 100644
--- a/xgraph/idraw.c
+++ b/xgraph/idraw.c
@@ -7,6 +7,7 @@
  */
 
 #include <stdio.h>
+#include <string.h>
 #include <X11/Xlib.h>
 #include "hard_devices.h"
 #include "xgout.h"
diff --git a/xgraph/tgif.c b/xgraph/tgif.c
index b4fac94ab..40e1aa1ca 100644
--- a/xgraph/tgif.c
+++ b/xgraph/tgif.c
@@ -5,6 +5,7 @@
  */
 
 #include <stdio.h>
+#include <string.h> /* for strlen() */
 #include <X11/Xlib.h>
 #include "hard_devices.h"
 #include "xgout.h"
diff --git a/xgraph/xtb.c b/xgraph/xtb.c
index 637cc2b45..92a19fbe4 100644
--- a/xgraph/xtb.c
+++ b/xgraph/xtb.c
@@ -12,10 +12,11 @@
  * want to use any of the standards yet -- they are too unstable).
  */
 
+#include <stdio.h>  /* for printf() */
 #include <X11/Xos.h>
 #include <X11/Xlib.h>
 #include <X11/Xutil.h>
-#include <string.h>  /* for strcpy */
+#include <string.h>  /* for strcpy() and strlen() */
 #include "xtb.h"
 
 extern void abort();