diff --git a/prism/src/explicit/AccumulationProduct.java b/prism/src/explicit/AccumulationProduct.java
index 01071919..86150f9b 100644
--- a/prism/src/explicit/AccumulationProduct.java
+++ b/prism/src/explicit/AccumulationProduct.java
@@ -62,6 +62,7 @@ public abstract class AccumulationProduct<M extends Model,Component> extends Pro
         int factorNr = 0;
         for (AccumulationFactor factor : ctx.accexp.getConstraint().getFactors()) {
                 lhs += factor.getFactor().evaluateInt(ctx.mc.getConstantValues()) * track.getWeight(factorNr);
+                factorNr++;
         }
 
         // Check the bound