diff --git a/tools/skpdiff/SkDiffContext.cpp b/tools/skpdiff/SkDiffContext.cpp
index 78d8400..4248ca3 100644
--- a/tools/skpdiff/SkDiffContext.cpp
+++ b/tools/skpdiff/SkDiffContext.cpp
@@ -289,6 +289,7 @@
         runnableDiffs[x].setup(this, baselineEntries[x], testEntries[x]);
         tg.add(&runnableDiffs[x]);
     }
+    tg.wait();
 }
 
 void SkDiffContext::outputRecords(SkWStream& stream, bool useJSONP) {