diff --git a/workspace_tools/build.py b/workspace_tools/build.py
index 1cf2eb4acb..bcd11c6138 100644
--- a/workspace_tools/build.py
+++ b/workspace_tools/build.py
@@ -120,3 +120,4 @@ if __name__ == '__main__':
     if failures:
         print "\n\nBuild failures:"
         print "\n".join(["  * %s" % f for f in failures])
+        sys.exit(1)