diff --git a/panda/src/pipeline/pipelineCyclerTrueImpl.cxx b/panda/src/pipeline/pipelineCyclerTrueImpl.cxx
index ed2c9bd479..d22ec68f01 100644
--- a/panda/src/pipeline/pipelineCyclerTrueImpl.cxx
+++ b/panda/src/pipeline/pipelineCyclerTrueImpl.cxx
@@ -341,6 +341,7 @@ set_num_stages(int num_stages) {
 ////////////////////////////////////////////////////////////////////
 void PipelineCyclerTrueImpl::CyclerMutex::
 output(ostream &out) const {
+  out << "CyclerMutex ";
   _cycler->cheat()->output(out);
 }
 #endif  // DEBUG_THREADS