diff --git a/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/DefaultFlowExecutionRepository.java b/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/DefaultFlowExecutionRepository.java
index 752afd12..61d83934 100644
--- a/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/DefaultFlowExecutionRepository.java
+++ b/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/DefaultFlowExecutionRepository.java
@@ -132,17 +132,27 @@ public class DefaultFlowExecutionRepository extends AbstractSnapshottingFlowExec
 
 	public void updateFlowExecutionSnapshot(FlowExecution execution) {
 		FlowExecutionKey key = execution.getKey();
+		if (key == null) {
+			return;
+		}
 		Conversation conversation = getConversation(key);
 		getSnapshotGroup(conversation).updateSnapshot(getSnapshotId(key), snapshot(execution));
 	}
 
 	public void removeFlowExecutionSnapshot(FlowExecution execution) {
 		FlowExecutionKey key = execution.getKey();
+		if (key == null) {
+			return;
+		}
 		Conversation conversation = getConversation(key);
 		getSnapshotGroup(conversation).removeSnapshot(getSnapshotId(key));
 	}
 
 	public void removeAllFlowExecutionSnapshots(FlowExecution execution) {
+		FlowExecutionKey key = execution.getKey();
+		if (key == null) {
+			return;
+		}
 		Conversation conversation = getConversation(execution.getKey());
 		getSnapshotGroup(conversation).removeAllSnapshots();
 	}
diff --git a/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/FlowExecutionSnapshotGroup.java b/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/FlowExecutionSnapshotGroup.java
index c52f845b..087cca12 100644
--- a/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/FlowExecutionSnapshotGroup.java
+++ b/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/FlowExecutionSnapshotGroup.java
@@ -30,22 +30,20 @@ public interface FlowExecutionSnapshotGroup {
 	public void addSnapshot(Serializable snapshotId, FlowExecutionSnapshot snapshot);
 
 	/**
-	 * Update the snapshot with the given id.
+	 * Update the snapshot with the given id. Does nothing if no snapshot has been added with the id provided.
 	 * @param snapshotId the snapshot id
 	 * @param snapshot the new snapshot
-	 * @throws SnapshotNotFoundException if there was no previous snapshot to update
 	 */
-	public void updateSnapshot(Serializable snapshotId, FlowExecutionSnapshot snapshot)
-			throws SnapshotNotFoundException;
+	public void updateSnapshot(Serializable snapshotId, FlowExecutionSnapshot snapshot);
 
 	/**
-	 * Remove the snapshot with the given id.
+	 * Remove the snapshot with the given id. Does nothing if no snapshot has been added with the id provided.
 	 * @param snapshotId the continuation id
 	 */
 	public void removeSnapshot(Serializable snapshotId);
 
 	/**
-	 * Remove all snapshots in this group.
+	 * Remove all snapshots in this group. Does nothing if no snapshots have been added to this group.
 	 */
 	public void removeAllSnapshots();
 
diff --git a/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/SimpleFlowExecutionSnapshotGroup.java b/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/SimpleFlowExecutionSnapshotGroup.java
index 0fb62506..642c7f74 100644
--- a/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/SimpleFlowExecutionSnapshotGroup.java
+++ b/spring-webflow/src/main/java/org/springframework/webflow/execution/repository/impl/SimpleFlowExecutionSnapshotGroup.java
@@ -87,10 +87,9 @@ class SimpleFlowExecutionSnapshotGroup implements FlowExecutionSnapshotGroup, Se
 		}
 	}
 
-	public void updateSnapshot(Serializable snapshotId, FlowExecutionSnapshot snapshot)
-			throws SnapshotNotFoundException {
+	public void updateSnapshot(Serializable snapshotId, FlowExecutionSnapshot snapshot) {
 		if (!snapshots.containsKey(snapshotId)) {
-			throw new SnapshotNotFoundException(snapshotId);
+			return;
 		}
 		snapshots.put(snapshotId, snapshot);
 	}