diff --git a/changelog/3292.fixed.md b/changelog/3292.fixed.md
new file mode 100644
index 000000000..4d3df66b0
--- /dev/null
+++ b/changelog/3292.fixed.md
@@ -0,0 +1 @@
+- Fixed a bug in `STTMuteFilter` where the user was not always muted during function calls, especially when there were multiple simultaneous calls.
diff --git a/src/pipecat/processors/filters/stt_mute_filter.py b/src/pipecat/processors/filters/stt_mute_filter.py
index 0b822b54a..8a0dca17d 100644
--- a/src/pipecat/processors/filters/stt_mute_filter.py
+++ b/src/pipecat/processors/filters/stt_mute_filter.py
@@ -21,8 +21,9 @@ from pipecat.frames.frames import (
     BotStartedSpeakingFrame,
     BotStoppedSpeakingFrame,
     Frame,
-    FunctionCallInProgressFrame,
+    FunctionCallCancelFrame,
     FunctionCallResultFrame,
+    FunctionCallsStartedFrame,
     InputAudioRawFrame,
     InterimTranscriptionFrame,
     InterruptionFrame,
@@ -116,7 +117,7 @@ class STTMuteFilter(FrameProcessor):
         self._config = config
         self._first_speech_handled = False
         self._bot_is_speaking = False
-        self._function_call_in_progress = False
+        self._function_call_in_progress = set()
         self._is_muted = False
 
     async def _handle_mute_state(self, should_mute: bool):
@@ -176,11 +177,12 @@ class STTMuteFilter(FrameProcessor):
         # Process frames to determine mute state
         if isinstance(frame, StartFrame):
             should_mute = await self._should_mute()
-        elif isinstance(frame, FunctionCallInProgressFrame):
-            self._function_call_in_progress = True
+        elif isinstance(frame, FunctionCallsStartedFrame):
+            for f in frame.function_calls:
+                self._function_call_in_progress.add(f.tool_call_id)
             should_mute = await self._should_mute()
-        elif isinstance(frame, FunctionCallResultFrame):
-            self._function_call_in_progress = False
+        elif isinstance(frame, (FunctionCallCancelFrame, FunctionCallResultFrame)):
+            self._function_call_in_progress.remove(frame.tool_call_id)
             should_mute = await self._should_mute()
         elif isinstance(frame, BotStartedSpeakingFrame):
             self._bot_is_speaking = True
diff --git a/tests/test_stt_mute_filter.py b/tests/test_stt_mute_filter.py
index 2bd041b65..c36693259 100644
--- a/tests/test_stt_mute_filter.py
+++ b/tests/test_stt_mute_filter.py
@@ -9,8 +9,10 @@ import unittest
 from pipecat.frames.frames import (
     BotStartedSpeakingFrame,
     BotStoppedSpeakingFrame,
+    FunctionCallFromLLM,
     FunctionCallInProgressFrame,
     FunctionCallResultFrame,
+    FunctionCallsStartedFrame,
     InputAudioRawFrame,
     InterimTranscriptionFrame,
     TranscriptionFrame,
@@ -148,54 +150,59 @@ class TestSTTMuteFilter(unittest.IsolatedAsyncioTestCase):
             expected_down_frames=expected_returned_frames,
         )
 
-    # TODO: Revisit once we figure out how to test SystemFrames and DataFrames
-    # async def test_function_call_strategy(self):
-    #     filter = STTMuteFilter(config=STTMuteConfig(strategies={STTMuteStrategy.FUNCTION_CALL}))
+    async def test_function_call_strategy(self):
+        filter = STTMuteFilter(config=STTMuteConfig(strategies={STTMuteStrategy.FUNCTION_CALL}))
 
-    #     frames_to_send = [
-    #         VADUserStartedSpeakingFrame(),  # Should pass through initially
-    #         UserStartedSpeakingFrame(),  # Should pass through initially
-    #         VADUserStoppedSpeakingFrame(),
-    #         UserStoppedSpeakingFrame(),
-    #         FunctionCallInProgressFrame(
-    #             function_name="get_weather",
-    #             tool_call_id="call_123",
-    #             arguments='{"location": "San Francisco"}',
-    #         ),  # Start function call
-    #         VADUserStartedSpeakingFrame(),  # Should be suppressed
-    #         UserStartedSpeakingFrame(),  # Should be suppressed
-    #         VADUserStoppedSpeakingFrame(),  # Should be suppressed
-    #         UserStoppedSpeakingFrame(),  # Should be suppressed
-    #         FunctionCallResultFrame(
-    #             function_name="get_weather",
-    #             tool_call_id="call_123",
-    #             arguments='{"location": "San Francisco"}',
-    #             result={"temperature": 22},
-    #         ),  # End function call
-    #         VADUserStartedSpeakingFrame(),  # Should pass through again
-    #         UserStartedSpeakingFrame(),  # Should pass through again
-    #         VADUserStoppedSpeakingFrame(),
-    #         UserStoppedSpeakingFrame(),
-    #     ]
+        frames_to_send = [
+            VADUserStartedSpeakingFrame(),  # Should pass through initially
+            UserStartedSpeakingFrame(),  # Should pass through initially
+            VADUserStoppedSpeakingFrame(),  # Should pass through initially
+            UserStoppedSpeakingFrame(),  # Should pass through initially
+            FunctionCallsStartedFrame(
+                function_calls=[
+                    FunctionCallFromLLM(
+                        function_name="get_weather",
+                        tool_call_id="call_123",
+                        arguments='{"location": "San Francisco"}',
+                        context=None,
+                    )
+                ]
+            ),  # Start function call
+            VADUserStartedSpeakingFrame(),  # Should be suppressed
+            UserStartedSpeakingFrame(),  # Should be suppressed
+            VADUserStoppedSpeakingFrame(),  # Should be suppressed
+            UserStoppedSpeakingFrame(),  # Should be suppressed
+            FunctionCallResultFrame(
+                function_name="get_weather",
+                tool_call_id="call_123",
+                arguments='{"location": "San Francisco"}',
+                result={"temperature": 22},
+            ),  # End function call
+            SleepFrame(),
+            VADUserStartedSpeakingFrame(),  # Should pass through again
+            UserStartedSpeakingFrame(),  # Should pass through again
+            VADUserStoppedSpeakingFrame(),
+            UserStoppedSpeakingFrame(),
+        ]
 
-    #     expected_returned_frames = [
-    #         VADUserStartedSpeakingFrame,
-    #         UserStartedSpeakingFrame,
-    #         VADUserStoppedSpeakingFrame,
-    #         UserStoppedSpeakingFrame,
-    #         FunctionCallInProgressFrame,
-    #         FunctionCallResultFrame,
-    #         VADUserStartedSpeakingFrame,
-    #         UserStartedSpeakingFrame,
-    #         VADUserStoppedSpeakingFrame,
-    #         UserStoppedSpeakingFrame,
-    #     ]
+        expected_returned_frames = [
+            VADUserStartedSpeakingFrame,
+            UserStartedSpeakingFrame,
+            VADUserStoppedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+            FunctionCallsStartedFrame,
+            FunctionCallResultFrame,
+            VADUserStartedSpeakingFrame,
+            UserStartedSpeakingFrame,
+            VADUserStoppedSpeakingFrame,
+            UserStoppedSpeakingFrame,
+        ]
 
-    #     await run_test(
-    #         filter,
-    #         frames_to_send=frames_to_send,
-    #         expected_down_frames=expected_returned_frames,
-    #     )
+        await run_test(
+            filter,
+            frames_to_send=frames_to_send,
+            expected_down_frames=expected_returned_frames,
+        )
 
     async def test_mute_until_first_bot_complete_strategy(self):
         filter = STTMuteFilter(