diff --git a/src/xo-misc.c b/src/xo-misc.c
index 6f0528c..c2582c7 100644
--- a/src/xo-misc.c
+++ b/src/xo-misc.c
@@ -2441,8 +2441,8 @@ void encode_uri(gchar *encoded_uri, gint bufsize, const gchar *uri)
       if (k + 4 >= bufsize)
         break;
       encoded_uri[k++] = '%';
-      encoded_uri[k++] = hexa[uri[i] / 16];
-      encoded_uri[k++] = hexa[uri[i] % 16];
+      encoded_uri[k++] = hexa[(unsigned char)uri[i] / 16];
+      encoded_uri[k++] = hexa[(unsigned char)uri[i] % 16];
     }
   }
   encoded_uri[k] = 0;