diff --git a/mediapipe/framework/calculator_graph.cc b/mediapipe/framework/calculator_graph.cc
index b9fc4c965..2a2088c6b 100644
--- a/mediapipe/framework/calculator_graph.cc
+++ b/mediapipe/framework/calculator_graph.cc
@@ -839,6 +839,10 @@ absl::Status CalculatorGraph::PrepareForRun(
 }
 
 absl::Status CalculatorGraph::WaitUntilIdle() {
+  if (has_sources_) {
+    LOG(WARNING) << "WaitUntilIdle called on a graph with source nodes, which "
+                    "is not fully supported at the moment.";
+  }
   MP_RETURN_IF_ERROR(scheduler_.WaitUntilIdle());
   VLOG(2) << "Scheduler idle.";
   absl::Status status = absl::OkStatus();
diff --git a/mediapipe/framework/calculator_graph.h b/mediapipe/framework/calculator_graph.h
index 354694e39..748d2fb32 100644
--- a/mediapipe/framework/calculator_graph.h
+++ b/mediapipe/framework/calculator_graph.h
@@ -229,8 +229,11 @@ class CalculatorGraph {
   // Wait until the running graph is in the idle mode, which is when nothing can
   // be scheduled and nothing is running in the worker threads. This function
   // can be called only after StartRun().
+  //
   // NOTE: The graph must not have any source nodes because source nodes prevent
   // the running graph from becoming idle until the source nodes are done.
+  // Currently, `WaitUntilIdle` cannot be used reliably on graphs with any
+  // source nodes.
   absl::Status WaitUntilIdle();
 
   // Wait until a packet is emitted on one of the observed output streams.
diff --git a/mediapipe/framework/scheduler.cc b/mediapipe/framework/scheduler.cc
index 854c10fd5..ceadce787 100644
--- a/mediapipe/framework/scheduler.cc
+++ b/mediapipe/framework/scheduler.cc
@@ -273,8 +273,8 @@ absl::Status Scheduler::WaitForObservedOutput() {
 // Idleness requires:
 // 1. either the graph has no source nodes or all source nodes are closed, and
 // 2. no packets are added to graph input streams.
-// For simplicity, we only allow WaitUntilIdle() to be called on a graph with
-// no source nodes. (This is enforced by CalculatorGraph::WaitUntilIdle().)
+// For simplicity, we only fully support WaitUntilIdle() to be called on a graph
+// with no source nodes.
 // The application must ensure no other threads are adding packets to graph
 // input streams while a WaitUntilIdle() call is in progress.
 absl::Status Scheduler::WaitUntilIdle() {