1 files changed, 2 insertions, 2 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcCompileAction.java b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcCompileAction.java
index 55e1baefff..f8ee247c7f 100644
--- a/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcCompileAction.java
+++ b/src/main/java/com/google/devtools/build/lib/rules/objc/ObjcCompileAction.java
@@ -186,8 +186,8 @@ public class ObjcCompileAction extends SpawnAction {
     return true;
   }
 
-  @Override
-  public Iterable<Artifact> discoverInputs(ActionExecutionContext actionExecutionContext)
+  public synchronized Iterable<Artifact> discoverInputs(
+      ActionExecutionContext actionExecutionContext)
       throws ActionExecutionException, InterruptedException {
     if (headersListFile != null) {
       discoveredInputs = findRequiredHeaderInputs();