diff --git a/prism/src/explicit/rewards/MDPRewardsSimple.java b/prism/src/explicit/rewards/MDPRewardsSimple.java
index 7564bf81..191d256a 100644
--- a/prism/src/explicit/rewards/MDPRewardsSimple.java
+++ b/prism/src/explicit/rewards/MDPRewardsSimple.java
@@ -61,6 +61,9 @@ public class MDPRewardsSimple implements MDPRewards
 	 */
 	public void setStateReward(int s, double r)
 	{
+		// Nothing to do for zero reward
+		if (r == 0.0)
+			return;
 		// If no rewards array created yet, create it
 		if (stateRewards == null) {
 			stateRewards = new ArrayList<Double>(numStates);
@@ -77,6 +80,9 @@ public class MDPRewardsSimple implements MDPRewards
 	public void setTransitionReward(int s, int i, double r)
 	{
 		List<Double> list;
+		// Nothing to do for zero reward
+		if (r == 0.0)
+			return;
 		// If no rewards array created yet, create it
 		if (transRewards == null) {
 			transRewards = new ArrayList<List<Double>>(numStates);
@@ -101,6 +107,17 @@ public class MDPRewardsSimple implements MDPRewards
 		list.set(i, r);
 	}
 
+	/**
+	 * Clear all rewards for state s.
+	 */
+	public void clearRewards(int s)
+	{
+		setStateReward(s, 0.0);
+		if (transRewards != null && transRewards.size() > s) {
+			transRewards.set(s, null);
+		}
+	}
+	
 	// Accessors
 	
 	@Override
diff --git a/prism/src/explicit/rewards/STPGRewardsSimple.java b/prism/src/explicit/rewards/STPGRewardsSimple.java
index a7dfcce2..224b3ee6 100644
--- a/prism/src/explicit/rewards/STPGRewardsSimple.java
+++ b/prism/src/explicit/rewards/STPGRewardsSimple.java
@@ -57,6 +57,9 @@ public class STPGRewardsSimple extends MDPRewardsSimple implements STPGRewards
 	public void setNestedTransitionReward(int s, int i, double r)
 	{
 		List<Double> list;
+		// Nothing to do for zero reward
+		if (r == 0.0)
+			return;
 		// If no rewards array created yet, create it
 		if (nestedTransRewards1 == null) {
 			nestedTransRewards1 = new ArrayList<List<Double>>(numStates);
@@ -88,6 +91,9 @@ public class STPGRewardsSimple extends MDPRewardsSimple implements STPGRewards
 	{
 		List<List<Double>> list1;
 		List<Double> list2;
+		// Nothing to do for zero reward
+		if (r == 0.0)
+			return;
 		// If no rewards array created yet, create it
 		if (nestedTransRewards2 == null) {
 			nestedTransRewards2 = new ArrayList<List<List<Double>>>(numStates);
@@ -126,6 +132,20 @@ public class STPGRewardsSimple extends MDPRewardsSimple implements STPGRewards
 		list2.set(j, r);
 	}
 
+	/**
+	 * Clear all rewards for state s.
+	 */
+	public void clearRewards(int s)
+	{
+		super.clearRewards(s);
+		if (nestedTransRewards1 != null && nestedTransRewards1.size() > s) {
+			nestedTransRewards1.set(s, null);
+		}
+		if (nestedTransRewards2 != null && nestedTransRewards2.size() > s) {
+			nestedTransRewards2.set(s, null);
+		}
+	}
+	
 	// Accessors
 	
 	@Override
diff --git a/prism/src/explicit/rewards/StateRewardsSimple.java b/prism/src/explicit/rewards/StateRewardsSimple.java
index c0a33592..4b7a0e93 100644
--- a/prism/src/explicit/rewards/StateRewardsSimple.java
+++ b/prism/src/explicit/rewards/StateRewardsSimple.java
@@ -54,6 +54,9 @@ public class StateRewardsSimple extends StateRewards
 	 */
 	public void setStateReward(int s, double r)
 	{
+		// Nothing to do for zero reward
+		if (r == 0.0)
+			return;
 		// If list not big enough, extend
 		int n = s - stateRewards.size() + 1;
 		if (n > 0) {