diff --git a/prism/src/explicit/IndexedSet.java b/prism/src/explicit/IndexedSet.java
index 5ec13279..837e4cfa 100644
--- a/prism/src/explicit/IndexedSet.java
+++ b/prism/src/explicit/IndexedSet.java
@@ -48,6 +48,11 @@ public class IndexedSet<T>
 		indexOfLastAdd = -1;
 	}
 
+	public void clear()
+	{
+		set.clear();
+	}
+	
 	public boolean add(T state)
 	{
 		Integer i = set.get(state);
diff --git a/prism/src/pta/Modules2PTA.java b/prism/src/pta/Modules2PTA.java
index dfe92482..959d6a22 100644
--- a/prism/src/pta/Modules2PTA.java
+++ b/prism/src/pta/Modules2PTA.java
@@ -592,6 +592,8 @@ public class Modules2PTA
 		}
 		// Catch a (possibly) common source of mem-out errors during explicit-state reachability
 		catch (OutOfMemoryError e) {
+			states.clear();
+			System.gc();
 			throw new PrismLangException("Out of memory after exploring " + (src + 1) + " states of module " + module.getName(), module);
 		}