diff --git a/lldb/source/Commands/CommandObjectExpression.cpp b/lldb/source/Commands/CommandObjectExpression.cpp
index 197bffe9c982f..41bc8abf4897f 100644
--- a/lldb/source/Commands/CommandObjectExpression.cpp
+++ b/lldb/source/Commands/CommandObjectExpression.cpp
@@ -640,9 +640,15 @@ void CommandObjectExpression::DoExecute(llvm::StringRef command,
             repl_sp->SetValueObjectDisplayOptions(m_varobj_options);
           }
 
+          if (!expr.empty()) {
+            result.GetOutputStream().Printf(
+                "Warning: trailing input is ignored in --repl mode\n");
+          }
+
           IOHandlerSP io_handler_sp(repl_sp->GetIOHandler());
           io_handler_sp->SetIsDone(false);
           debugger.RunIOHandlerAsync(io_handler_sp);
+          return;
         } else {
           repl_error = Status::FromErrorStringWithFormat(
               "Couldn't create a REPL for %s",
diff --git a/lldb/test/API/repl/clang/TestClangREPL.py b/lldb/test/API/repl/clang/TestClangREPL.py
index 97d91d1b8f7a5..ffa598b650937 100644
--- a/lldb/test/API/repl/clang/TestClangREPL.py
+++ b/lldb/test/API/repl/clang/TestClangREPL.py
@@ -30,8 +30,9 @@ def start_repl(self):
         self.expect("b main", substrs=["Breakpoint 1", "address ="])
         self.expect("run", substrs=["stop reason = breakpoint 1"])
 
-        # Start the REPL.
-        self.child.send("expression --repl -l c --\n")
+        # Start the REPL with a harmless trailing input to trigger the warning.
+        self.child.send("expression --repl -l c -- 3 + 3\n")
+        self.child.expect_exact("Warning: trailing input is ignored in --repl mode")
         self.child.expect_exact("1>")
 
     # PExpect uses many timeouts internally and doesn't play well