diff --git a/src/x11/xprops.c b/src/x11/xprops.c
index be3882455..e3bd931f0 100644
--- a/src/x11/xprops.c
+++ b/src/x11/xprops.c
@@ -194,6 +194,7 @@ async_get_property_finish (xcb_connection_t          *xcb_conn,
 {
   xcb_get_property_reply_t *reply;
   xcb_generic_error_t *error;
+  int length;
 
   reply = xcb_get_property_reply (xcb_conn, cookie, &error);
   if (error)
@@ -209,8 +210,15 @@ async_get_property_finish (xcb_connection_t          *xcb_conn,
   results->prop = NULL;
 
   if (results->type != None)
-    results->prop = g_memdup (xcb_get_property_value (reply),
-                              xcb_get_property_value_length (reply));
+    {
+      length = xcb_get_property_value_length (reply);
+      /* Leave room for a trailing '\0' since xcb doesn't return null-terminated
+       * strings
+       */
+      results->prop = g_malloc (length + 1);
+      memcpy (results->prop, xcb_get_property_value (reply), length);
+      results->prop[length] = '\0';
+    }
 
   free (reply);
   return (results->prop != NULL);