diff --git a/src/claude_code_sdk/_internal/transport/subprocess_cli.py b/src/claude_code_sdk/_internal/transport/subprocess_cli.py
index 47bcad7..4d6edce 100644
--- a/src/claude_code_sdk/_internal/transport/subprocess_cli.py
+++ b/src/claude_code_sdk/_internal/transport/subprocess_cli.py
@@ -157,7 +157,7 @@ class SubprocessCLITransport(Transport):
             cmd.extend(["--input-format", "stream-json"])
         else:
             # String mode: use --print with the prompt
-            cmd.extend(["--print", str(self._prompt)])
+            cmd.extend(["--print", "--", str(self._prompt)])
 
         return cmd