diff --git a/python/plugins/processing/algs/qgis/Dissolve.py b/python/plugins/processing/algs/qgis/Dissolve.py
index d2ada9bb075..871a41f9db3 100644
--- a/python/plugins/processing/algs/qgis/Dissolve.py
+++ b/python/plugins/processing/algs/qgis/Dissolve.py
@@ -130,6 +130,7 @@ class Dissolve(GeoAlgorithm):
 
             features = None
 
+            nElement = 0
             for key, value in myDict.items():
                 nElement += 1
                 progress.setPercentage(int(nElement * 100 / nFeat))