diff --git a/aiida_flexpart/calculations/flexpart_post.py b/aiida_flexpart/calculations/flexpart_post.py
index ea19bb3..8d8fe55 100644
--- a/aiida_flexpart/calculations/flexpart_post.py
+++ b/aiida_flexpart/calculations/flexpart_post.py
@@ -6,7 +6,7 @@
 from aiida import orm, common, engine
 
 
-class PostProcessingCalculation(CalcJob):
+class PostProcessingCalculation(engine.CalcJob):
     """AiiDA calculation plugin for post processing."""
     @classmethod
     def define(cls, spec):
@@ -39,14 +39,14 @@ def prepare_for_submission(self, folder):
         if 'input_offline_dir' in self.inputs:
             params += ['-n',self.inputs.input_offline_dir.get_remote_path()]
 
-        codeinfo = datastructures.CodeInfo()
+        codeinfo = common.CodeInfo()
         codeinfo.cmdline_params = params
         codeinfo.code_uuid = self.inputs.code.uuid
         codeinfo.stdout_name = self.metadata.options.output_filename
         codeinfo.withmpi = self.inputs.metadata.options.withmpi
 
         # Prepare a `CalcInfo` to be returned to the engine
-        calcinfo = datastructures.CalcInfo()
+        calcinfo = common.CalcInfo()
         calcinfo.codes_info = [codeinfo]
         calcinfo.retrieve_list = ['grid_time_*.nc', 'boundary_sensitivity_*.nc', 'aiida.out']
 
diff --git a/aiida_flexpart/parsers/flexpart_post.py b/aiida_flexpart/parsers/flexpart_post.py
index 967bc1f..5ca2168 100644
--- a/aiida_flexpart/parsers/flexpart_post.py
+++ b/aiida_flexpart/parsers/flexpart_post.py
@@ -6,10 +6,10 @@
 """
 from aiida import engine, parsers, plugins, common, orm
 
-FlexpartCalculation = CalculationFactory('flexpart.post')
+FlexpartCalculation = plugins.CalculationFactory('flexpart.post')
 
 
-class FlexpartPostParser(Parser):
+class FlexpartPostParser(parsers.Parser):
     """
     Parser class for parsing output of calculation.
     """
@@ -24,7 +24,7 @@ def __init__(self, node):
         """
         super().__init__(node)
         if not issubclass(node.process_class, FlexpartCalculation):
-            raise exceptions.ParsingError('Can only parse FlexpartCalculation')
+            raise common.ParsingError('Can only parse FlexpartCalculation')
 
     def parse(self, **kwargs):
         """
@@ -39,14 +39,15 @@ def parse(self, **kwargs):
         files_expected = [output_filename]
         # Note: set(A) <= set(B) checks whether A is a subset of B
         if not set(files_expected) <= set(files_retrieved):
-            self.logger.error("Found files '{}', expected to find '{}'".format(
-                files_retrieved, files_expected))
+            self.logger.error(
+                f"Found files '{files_retrieved}', expected to find '{files_expected}'"
+            )
             return self.exit_codes.ERROR_MISSING_OUTPUT_FILES
 
         # add output file
-        self.logger.info("Parsing '{}'".format(output_filename))
+        self.logger.info(f"Parsing '{output_filename}'")
         with self.retrieved.open(output_filename, 'rb') as handle:
-            output_node = SinglefileData(file=handle)
+            output_node = orm.SinglefileData(file=handle)
         self.out('output_file', output_node)
 
-        return ExitCode(0)
+        return engine.ExitCode(0)