diff --git a/Source/CTest/cmCTestLaunch.cxx b/Source/CTest/cmCTestLaunch.cxx
index 9669d76a32..cbe53a7705 100644
--- a/Source/CTest/cmCTestLaunch.cxx
+++ b/Source/CTest/cmCTestLaunch.cxx
@@ -152,6 +152,9 @@ void cmCTestLaunch::RunChild()
   cmUVProcessChainBuilder builder;
   builder.AddCommand(this->RealArgV);
 
+  // We always share the input pipe.
+  builder.SetExternalStream(cmUVProcessChainBuilder::Stream_INPUT, stdin);
+
   cmsys::ofstream fout;
   cmsys::ofstream ferr;
   if (this->Reporter.Passthru) {