diff --git a/distiller/pruning/ranked_structures_pruner.py b/distiller/pruning/ranked_structures_pruner.py
index 4691ede991e2919b35f9aea4573790385dec042f..629df73f4de52907b285eea4fa11e994a0bbe10b 100755
--- a/distiller/pruning/ranked_structures_pruner.py
+++ b/distiller/pruning/ranked_structures_pruner.py
@@ -348,7 +348,7 @@ class ActivationRankedFilterPruner(_RankedStructureParameterPruner):
             raise ValueError("Could not find a layer named %s in the model."
                              "\nMake sure to use assign_layer_fq_names()" % fq_name)
         if not hasattr(module, self.activation_rank_criterion):
-            raise ValueError("Could not find attribute \"{}\" in module %s"
+            raise ValueError("Could not find attribute \"{}\" in module {}"
                              "\nMake sure to use SummaryActivationStatsCollector(\"{}\")".
                              format(self.activation_rank_criterion, fq_name, self.activation_rank_criterion))