diff --git a/Simulation/Aivika/Experiment/Types.hs b/Simulation/Aivika/Experiment/Types.hs
--- a/Simulation/Aivika/Experiment/Types.hs
+++ b/Simulation/Aivika/Experiment/Types.hs
@@ -417,7 +417,7 @@
   containerData :: c a -> Event a
 
   -- | Get the signal for the container.
-  containerSignal :: c a => Maybe (Signal ())
+  containerSignal :: c a -> Maybe (Signal ())
 
 instance SeriesContainer Parameter where
 
diff --git a/aivika-experiment.cabal b/aivika-experiment.cabal
--- a/aivika-experiment.cabal
+++ b/aivika-experiment.cabal
@@ -1,5 +1,5 @@
 name:            aivika-experiment
-version:         1.3
+version:         1.3.1
 synopsis:        Simulation experiments for the Aivika library
 description:
     This package allows defining simulation experiments for the Aivika