diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2292a0f..4c1be2b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,11 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [4.0.4] - 2025-06-09
+
+- Fixed non-multichannel sessions bugging out after adding multichannel support
+
+
 ## [4.0.3] - 2025-06-06
 
 - Fixed microphone transcription tests not working after adding multichan dz support
diff --git a/VERSION b/VERSION
index aa31e71..7d666cb 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.0.3
\ No newline at end of file
+4.0.4
\ No newline at end of file
diff --git a/speechmatics/cli.py b/speechmatics/cli.py
index e34d4a1..bbdaac4 100755
--- a/speechmatics/cli.py
+++ b/speechmatics/cli.py
@@ -808,23 +808,12 @@ def rt_main(args):
         translation_config=transcription_config.translation_config,
     )
 
-    def run(stream=None, channel_stream_pairs=None):
+    def run(stream):
         try:
-            # Pass in either stream or channel_stream_pairs depending on what != None
-            # Dynamically construct the args based on the input
-            args_list = [transcription_config]
-            if stream is not None:
-                args_list.append(stream)
-            elif channel_stream_pairs is not None:
-                args_list.append(None)  # This skips the stream argument
-                args_list.append(channel_stream_pairs)
-            else:
-                raise SystemExit(
-                    "Neither stream nor channel_stream_pairs were provided."
-                )
             api.run_synchronously(
-                *args_list,
-                audio_settings=get_audio_settings(args),
+                stream,
+                transcription_config,
+                get_audio_settings(args),
                 from_cli=True,
                 extra_headers=extra_headers,
             )
@@ -860,7 +849,7 @@ def run(stream=None, channel_stream_pairs=None):
                 # Here the order matters, as stream positions and diarization labels correspond to one another.
                 channel_name = transcription_config.channel_diarization_labels[i]
                 channel_stream_pairs[channel_name] = args["files"][i]
-            run(channel_stream_pairs=channel_stream_pairs)
+            run(stream=channel_stream_pairs)
 
         else:
             for filename in args["files"]:
diff --git a/speechmatics/client.py b/speechmatics/client.py
index 93e3eaa..61a2554 100644
--- a/speechmatics/client.py
+++ b/speechmatics/client.py
@@ -9,6 +9,7 @@
 from collections import defaultdict
 from contextlib import AsyncExitStack
 import copy
+from io import IOBase
 import json
 import logging
 import os
@@ -521,9 +522,8 @@ async def _communicate(self, stream, audio_settings):
 
     async def run(
         self,
+        stream: Union[IOBase, Dict[str, IOBase]],
         transcription_config: TranscriptionConfig,
-        stream: Optional[Any] = None,
-        channel_stream_pairs=None,
         audio_settings: AudioSettings = None,
         from_cli: bool = False,
         extra_headers: Dict = None,
@@ -537,11 +537,8 @@ async def run(
         :param transcription_config: Configuration for the transcription.
         :type transcription_config: speechmatics.models.TranscriptionConfig
 
-        :param stream: Optional file-like object which an audio stream can be read from.
-        :type stream: io.IOBase
-
-        :param channel_stream_pairs: Optional dict containing channel-name stream pairs.
-        :type channel_stream_pairs dict[str, io.IOBase]
+        :param stream: Optional file-like object or Dict of file-likes which an audio stream can be read from.
+        :type stream: Union[IOBase, Dict[str, IOBase]],
 
         :param audio_settings: Configuration for the audio stream.
         :type audio_settings: speechmatics.models.AudioSettings
@@ -552,7 +549,14 @@ async def run(
         :raises Exception: Can raise any exception returned by the
             consumer/producer tasks.
         """
-        if channel_stream_pairs:
+        # Check we get either a dict or a file-like object
+        channel_stream_pairs = None
+        if isinstance(stream, dict):
+            # Case where stream is channel stream pairs
+            channel_stream_pairs = stream
+
+        # Set channel_stream pairs if provided
+        if channel_stream_pairs is not None:
             opened_streams = {}
             self._stream_exits = AsyncExitStack()
             for channel_name, path in channel_stream_pairs.items():
@@ -564,6 +568,7 @@ async def run(
             self.channel_stream_pairs = opened_streams
         else:
             self.channel_stream_pairs = None
+
         self.transcription_config = transcription_config
         self._language_pack_info = None
         await self._init_synchronization_primitives()