diff --git a/voice.py b/voice.py
index a3de111..8dd29f1 100644
--- a/voice.py
+++ b/voice.py
@@ -269,6 +269,8 @@ class VoiceSession:
 
             # Set caller's key(s) — decrypts incoming audio
             # Use all collected keys with their correct indices (Element Call may rotate)
+            # Also set as shared key fallback: Rust FFI may not use per-participant
+            # key for remote participants in all code paths.
             if self._caller_key:
                 caller_id = remote_identity or self._caller_identity
                 if caller_id:
@@ -276,6 +278,10 @@ class VoiceSession:
                     for idx, key in keys_to_set.items():
                         kp.set_key(caller_id, key, idx)
                         logger.info("Set caller key[%d] for %s (%d bytes)", idx, caller_id, len(key))
+                    # Shared key fallback: use highest-index caller key
+                    max_idx = max(keys_to_set.keys())
+                    kp.set_shared_key(keys_to_set[max_idx], max_idx)
+                    logger.info("Set shared key fallback[%d] (%d bytes)", max_idx, len(keys_to_set[max_idx]))
                 else:
                     logger.warning("Have caller key but no caller identity")
             else: