diff --git a/src/server/services/wms/qgswmsrenderer.cpp b/src/server/services/wms/qgswmsrenderer.cpp
index ca2c185c2be..e09c74d3901 100644
--- a/src/server/services/wms/qgswmsrenderer.cpp
+++ b/src/server/services/wms/qgswmsrenderer.cpp
@@ -232,6 +232,7 @@ namespace QgsWms
       painter->end();
     }
 
+    rootGroup.clear();
     return image.release();
   }