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 9957264c..e142d0ad 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
@@ -126,6 +126,7 @@ public class FlowExecutorImpl implements FlowExecutor {
 			ExternalContextHolder.setExternalContext(context);
 			FlowExecutionKey key = executionRepository.parseFlowExecutionKey(flowExecutionKey);
 			FlowExecutionLock lock = executionRepository.getLock(key);
+			lock.lock();
 			try {
 				FlowExecution flowExecution = executionRepository.getFlowExecution(key);
 				flowExecution.resume(context);
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 c4d8fde0..1a593b83 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
@@ -178,10 +178,10 @@ public class FlowExecutorImplTests extends TestCase {
 	}
 
 	private void replayMocks() {
-		EasyMock.replay(new Object[] { locator, definition, factory, execution, repository });
+		EasyMock.replay(new Object[] { locator, definition, factory, execution, repository, lock });
 	}
 
 	private void verifyMocks() {
-		EasyMock.verify(new Object[] { locator, definition, factory, execution, repository });
+		EasyMock.verify(new Object[] { locator, definition, factory, execution, repository, lock });
 	}
 }