diff --git a/src/polymarket/_internal/rfq.py b/src/polymarket/_internal/rfq.py
index 21382f3..b655880 100644
--- a/src/polymarket/_internal/rfq.py
+++ b/src/polymarket/_internal/rfq.py
@@ -451,6 +451,9 @@ def _handle_rfq_error(self, raw: dict[str, object]) -> None:
         request_type = raw.get("request_type")
         rfq_id = raw.get("rfq_id")
         quote_id = raw.get("quote_id")
+        error_id = raw.get("error_id")
+        if error_id is not None and not isinstance(error_id, str):
+            raise UnexpectedResponseError("Expected RFQ error_id to be a string.")
         code = _parse_error_code(raw.get("code"))
         message = raw.get("error")
         text = message if isinstance(message, str) else "RFQ request failed."
@@ -459,7 +462,7 @@ def _handle_rfq_error(self, raw: dict[str, object]) -> None:
                 raise TransportError("Uncorrelated RFQ quoter error.")
             self._reject(
                 _quote_ack_key(rfq_id),
-                RfqQuoteRejectedError(text, rfq_id=rfq_id, code=code),
+                RfqQuoteRejectedError(text, rfq_id=rfq_id, code=code, error_id=error_id),
             )
         elif request_type == "RFQ_QUOTE_CANCEL":
             if not isinstance(rfq_id, str) or not isinstance(quote_id, str):
@@ -471,6 +474,7 @@ def _handle_rfq_error(self, raw: dict[str, object]) -> None:
                     rfq_id=rfq_id,
                     quote_id=quote_id,
                     code=code,
+                    error_id=error_id,
                 ),
             )
         elif request_type == "RFQ_CONFIRMATION_RESPONSE":
@@ -483,6 +487,7 @@ def _handle_rfq_error(self, raw: dict[str, object]) -> None:
                     rfq_id=rfq_id,
                     quote_id=quote_id,
                     code=code,
+                    error_id=error_id,
                 ),
             )
 
diff --git a/src/polymarket/rfq.py b/src/polymarket/rfq.py
index d94118c..a8d855d 100644
--- a/src/polymarket/rfq.py
+++ b/src/polymarket/rfq.py
@@ -63,6 +63,8 @@ class RfqErrorCode(StrEnum):
     INVALID_RFQ = "INVALID_RFQ"
     INVALID_RFQ_STATE = "INVALID_RFQ_STATE"
     INVALID_ROLE = "INVALID_ROLE"
+    INVALID_SIGNATURE = "INVALID_SIGNATURE"
+    INTERNAL_ERROR = "INTERNAL_ERROR"
     LEG_METADATA_UNAVAILABLE = "LEG_METADATA_UNAVAILABLE"
     MAKER_ALREADY_RESPONDED = "MAKER_ALREADY_RESPONDED"
     MAKER_NOT_REQUIRED = "MAKER_NOT_REQUIRED"
@@ -170,10 +172,18 @@ async def decline(self) -> RfqConfirmationAck:
 
 
 class RfqQuoteRejectedError(PolymarketError):
-    def __init__(self, message: str, *, rfq_id: RfqId, code: RfqErrorCode | None = None) -> None:
+    def __init__(
+        self,
+        message: str,
+        *,
+        rfq_id: RfqId,
+        code: RfqErrorCode | None = None,
+        error_id: str | None = None,
+    ) -> None:
         super().__init__(message)
         self.rfq_id = rfq_id
         self.code = code
+        self.error_id = error_id
 
 
 class RfqCancelQuoteRejectedError(PolymarketError):
@@ -184,11 +194,13 @@ def __init__(
         rfq_id: RfqId,
         quote_id: RfqQuoteId,
         code: RfqErrorCode | None = None,
+        error_id: str | None = None,
     ) -> None:
         super().__init__(message)
         self.rfq_id = rfq_id
         self.quote_id = quote_id
         self.code = code
+        self.error_id = error_id
 
 
 class RfqConfirmationRejectedError(PolymarketError):
@@ -199,11 +211,13 @@ def __init__(
         rfq_id: RfqId,
         quote_id: RfqQuoteId,
         code: RfqErrorCode | None = None,
+        error_id: str | None = None,
     ) -> None:
         super().__init__(message)
         self.rfq_id = rfq_id
         self.quote_id = quote_id
         self.code = code
+        self.error_id = error_id
 
 
 @runtime_checkable
diff --git a/tests/integration/test_rfq.py b/tests/integration/test_rfq.py
index 02af98d..0a9686c 100644
--- a/tests/integration/test_rfq.py
+++ b/tests/integration/test_rfq.py
@@ -389,6 +389,7 @@ async def handler(ws: ServerConnection) -> None:
                         {
                             "type": "RFQ_ERROR",
                             "request_type": "RFQ_QUOTE",
+                            "error_id": "reqerr-1",
                             "rfq_id": RFQ_ID,
                             "code": code,
                             "error": "quote rejected",
@@ -406,6 +407,7 @@ async def handler(ws: ServerConnection) -> None:
             with pytest.raises(RfqQuoteRejectedError, match="quote rejected") as exc_info:
                 await event.quote(price=Decimal("0.45"))
             assert exc_info.value.code == code
+            assert exc_info.value.error_id == "reqerr-1"
             break