diff --git a/hw/dmx/examples/ev.c b/hw/dmx/examples/ev.c
index b70016a45..09e703ce7 100644
--- a/hw/dmx/examples/ev.c
+++ b/hw/dmx/examples/ev.c
@@ -56,7 +56,7 @@ main(int argc, char **argv)
     int fd = 0;
     int rc;
     int i, j;
-    char *tmp;
+    const char *tmp;
 
 #define test_bit(bit) (mask[(bit)/8] & (1 << ((bit)%8)))