diff --git a/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pxd b/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pxd
index f336a568387db..dd5fd71845a51 100644
--- a/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pxd
+++ b/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pxd
@@ -47,7 +47,6 @@ cdef class IntermediateOutputProcessor(OutputProcessor):
 cdef class FunctionOperation(Operation):
     cdef OutputProcessor _output_processor
     cdef bint _is_python_coder
-    cdef StreamCoderImpl _value_coder_impl
     cdef object process_element
     cdef object operation
     cdef object operation_cls
diff --git a/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pyx b/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pyx
index ed5d0ca7567ba..06fbce3b405f3 100644
--- a/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pyx
+++ b/flink-python/pyflink/fn_execution/beam/beam_operations_fast.pyx
@@ -111,7 +111,7 @@ cdef class FunctionOperation(Operation):
             self._output_processor = NetworkOutputProcessor(consumer)
 
             _value_coder_impl = consumer.windowed_coder.wrapped_value_coder.get_impl()._value_coder
-            if isinstance(self._value_coder_impl, FlinkLengthPrefixCoderBeamWrapper):
+            if isinstance(_value_coder_impl, FlinkLengthPrefixCoderBeamWrapper):
                 self._is_python_coder = False
             else:
                 self._is_python_coder = True