diff --git a/samples/docview/chart.xpm b/samples/docview/chart.xpm
index be27181d87..f1c0c5d43d 100644
--- a/samples/docview/chart.xpm
+++ b/samples/docview/chart.xpm
@@ -1,5 +1,5 @@
 /* XPM */
-static char *chrt_xpm[] = {
+static const char *chrt_xpm[] = {
 /* columns rows colors chars-per-pixel */
 "32 32 11 1",
 "  c black",
diff --git a/samples/docview/doc.xpm b/samples/docview/doc.xpm
index 7a60b89620..4ab82840b2 100644
--- a/samples/docview/doc.xpm
+++ b/samples/docview/doc.xpm
@@ -1,5 +1,5 @@
 /* XPM */
-static char *doc_xpm[] = {
+static const char *doc_xpm[] = {
 /* columns rows colors chars-per-pixel */
 "32 32 5 1",
 "  c black",
diff --git a/samples/docview/notepad.xpm b/samples/docview/notepad.xpm
index 4743183ea2..09d9cb237f 100644
--- a/samples/docview/notepad.xpm
+++ b/samples/docview/notepad.xpm
@@ -1,5 +1,5 @@
 /* XPM */
-static char *notepad_xpm[] = {
+static const char *notepad_xpm[] = {
 /* columns rows colors chars-per-pixel */
 "32 32 5 1",
 "  c black",