diff --git a/linux/devices/Max31865RtdLowlevelHandler.cpp b/linux/devices/Max31865RtdLowlevelHandler.cpp
index 4869fe39..f2815f5f 100644
--- a/linux/devices/Max31865RtdLowlevelHandler.cpp
+++ b/linux/devices/Max31865RtdLowlevelHandler.cpp
@@ -311,6 +311,9 @@ ReturnValue_t Max31865RtdReader::readReceivedMessage(CookieIF* cookie, uint8_t**
     return returnvalue::FAILED;
   }
   auto* rtdCookie = dynamic_cast<Max31865ReaderCookie*>(cookie);
+  if(rtdCookie == nullptr) {
+    return returnvalue::FAILED;
+  }
   uint8_t* exchangePtr = rtdCookie->exchangeBuf.data();
   size_t serLen = 0;
   auto result = rtdCookie->db.serialize(&exchangePtr, &serLen, rtdCookie->exchangeBuf.size(),