diff --git a/Projects/Athena/CMakeLists.txt b/Projects/Athena/CMakeLists.txt
index a3aecd1e639c3ddc25d00a56c42e20b9d0f5a8a1..d3b2c21a599c16a6b50ea0f7109abe62d8bc22f1 100644
--- a/Projects/Athena/CMakeLists.txt
+++ b/Projects/Athena/CMakeLists.txt
@@ -56,8 +56,9 @@ mark_as_advanced( TDAQ-COMMON_ATROOT TDAQ_PROJECT_NAME
 set( HEPMC3_USE TRUE CACHE BOOL "Build with HepMC3" )
 
 # Configure flake8:
-set( ATLAS_FLAKE8 flake8_atlas --select ATL,ATL902,F,E101,E7,E9,W6
-                               --ignore ATL9,E701,E702,E704,E741
+set( ATLAS_FLAKE8 flake8_atlas --isolated --select ATL,F,E101,E7,E9,W6
+                               --ignore E701,E702,E704,E741
+                               --enable-extensions ATL902
    CACHE STRING "Default flake8 command" )
 set( ATLAS_PYTHON_CHECKER ${ATLAS_FLAKE8}
    CACHE STRING "Python checker command to run during Python module compilation" )