diff --git a/spring-webflow/src/main/java/org/springframework/webflow/executor/FlowExecutorImpl.java b/spring-webflow/src/main/java/org/springframework/webflow/executor/FlowExecutorImpl.java
index c113ce2a..45fef518 100644
--- a/spring-webflow/src/main/java/org/springframework/webflow/executor/FlowExecutorImpl.java
+++ b/spring-webflow/src/main/java/org/springframework/webflow/executor/FlowExecutorImpl.java
@@ -139,7 +139,13 @@ public class FlowExecutorImpl implements FlowExecutor {
 			FlowExecution flowExecution = executionFactory.createFlowExecution(flowDefinition);
 			flowExecution.start(input, context);
 			if (!flowExecution.hasEnded()) {
-				executionRepository.putFlowExecution(flowExecution);
+				FlowExecutionLock lock = executionRepository.getLock(flowExecution.getKey());
+				lock.lock();
+				try {
+					executionRepository.putFlowExecution(flowExecution);
+				} finally {
+					lock.unlock();
+				}
 				return createPausedResult(flowExecution);
 			} else {
 				return createEndResult(flowExecution);
diff --git a/spring-webflow/src/test/java/org/springframework/webflow/executor/FlowExecutorImplTests.java b/spring-webflow/src/test/java/org/springframework/webflow/executor/FlowExecutorImplTests.java
index 65c556ef..cc851048 100644
--- a/spring-webflow/src/test/java/org/springframework/webflow/executor/FlowExecutorImplTests.java
+++ b/spring-webflow/src/test/java/org/springframework/webflow/executor/FlowExecutorImplTests.java
@@ -53,11 +53,19 @@ public class FlowExecutorImplTests extends TestCase {
 		execution.hasEnded();
 		EasyMock.expectLastCall().andReturn(Boolean.FALSE);
 
+		MockFlowExecutionKey flowExecutionKey = new MockFlowExecutionKey("12345");
+		EasyMock.expect(execution.getKey()).andReturn(flowExecutionKey);
+		EasyMock.expect(repository.getLock(flowExecutionKey)).andReturn(lock);
+
+		lock.lock();
+
 		repository.putFlowExecution(execution);
 
+		lock.unlock();
+
 		EasyMock.expect(execution.getDefinition()).andReturn(definition);
 		EasyMock.expect(definition.getId()).andReturn("foo");
-		EasyMock.expect(execution.getKey()).andReturn(new MockFlowExecutionKey("12345"));
+		EasyMock.expect(execution.getKey()).andReturn(flowExecutionKey);
 
 		replayMocks();