diff --git a/patch_3877-r11714.patch b/patch_3877-r11714.patch
index cc8f55b..5896375 100644
--- a/patch_3877-r11714.patch
+++ b/patch_3877-r11714.patch
@@ -1,6 +1,15 @@
 diff -urNad mapserver-6.0.0~/mapunion.c mapserver-6.0.0/mapunion.c
 --- mapserver-6.0.0/mapunion.c	(revision 11709)
 +++ mapserver-6.0.0/mapunion.c	(revision 11714)
+@@ -236,7 +236,7 @@
+ }
+
+ /* clean up expression tokens */
+-void msUnionLayerFreeExpressionTokens(layerObj *layer)
++int msUnionLayerFreeExpressionTokens(layerObj *layer)
+ {
+     int i,j;
+     freeExpressionTokens(&(layer->filter));
 @@ -316,5 +316,5 @@
              /* get items requested by the union layer plus the required items */
              msLayerSetProcessingKey(srclayer, "ITEMS", itemlist);