diff --git a/src/pipecat/services/speechmatics/tts.py b/src/pipecat/services/speechmatics/tts.py
index a4f99d03f..519e6775e 100644
--- a/src/pipecat/services/speechmatics/tts.py
+++ b/src/pipecat/services/speechmatics/tts.py
@@ -43,6 +43,9 @@ class SpeechmaticsTTSSettings(TTSSettings):
         max_retries: Maximum number of retries for HTTP requests.
     """
 
+    # Speechmatics requires a voice (the URL path includes it), so narrow
+    # the inherited TTSSettings.voice field to disallow None.
+    voice: str | _NotGiven = field(default_factory=lambda: NOT_GIVEN)
     max_retries: int | _NotGiven = field(default_factory=lambda: NOT_GIVEN)