diff --git a/prism/src/prism/NondetModelChecker.java b/prism/src/prism/NondetModelChecker.java
index dd6194e1..f882cde1 100644
--- a/prism/src/prism/NondetModelChecker.java
+++ b/prism/src/prism/NondetModelChecker.java
@@ -1290,7 +1290,7 @@ public class NondetModelChecker extends NonProbModelChecker
 		if (Expression.isReach(expr)) {
 			return checkRewardReach((ExpressionTemporal) expr, stateRewards, transRewards, min);
 		}
-		else if (Expression.isCoSafeLTLSyntactic(expr)) {
+		else if (Expression.isCoSafeLTLSyntactic(expr, true)) {
 			return checkRewardCoSafeLTL(expr, stateRewards, transRewards, min);
 		}
 		throw new PrismException("R operator contains a path formula that is not syntactically co-safe: " + expr);
diff --git a/prism/src/prism/ProbModelChecker.java b/prism/src/prism/ProbModelChecker.java
index 4cfbab0c..0174eabe 100644
--- a/prism/src/prism/ProbModelChecker.java
+++ b/prism/src/prism/ProbModelChecker.java
@@ -820,7 +820,7 @@ public class ProbModelChecker extends NonProbModelChecker
 		if (Expression.isReach(expr)) {
 			return checkRewardReach((ExpressionTemporal) expr, stateRewards, transRewards);
 		}
-		else if (Expression.isCoSafeLTLSyntactic(expr)) {
+		else if (Expression.isCoSafeLTLSyntactic(expr, true)) {
 			return checkRewardCoSafeLTL(expr, stateRewards, transRewards);
 		}
 		throw new PrismException("R operator contains a path formula that is not syntactically co-safe: " + expr);