diff --git a/tests/core/pyspec/eth2spec/test/conftest.py b/tests/core/pyspec/eth2spec/test/conftest.py
index 3026b48eb..e8478050f 100644
--- a/tests/core/pyspec/eth2spec/test/conftest.py
+++ b/tests/core/pyspec/eth2spec/test/conftest.py
@@ -1,6 +1,6 @@
 from eth2spec.test import context
 from eth2spec.test.helpers.constants import (
-    ALL_PHASES,
+    ALL_PHASES, ALLOWED_TEST_RUNNER_FORKS
 )
 from eth2spec.utils import bls as bls_utils
 
@@ -54,10 +54,10 @@ def pytest_addoption(parser):
 
 def _validate_fork_name(forks):
     for fork in forks:
-        if fork not in set(ALL_PHASES):
+        if fork not in set(ALLOWED_TEST_RUNNER_FORKS):
             raise ValueError(
                 f'The given --fork argument "{fork}" is not an available fork.'
-                f' The available forks: {ALL_PHASES}'
+                f' The available forks: {ALLOWED_TEST_RUNNER_FORKS}'
             )
 
 
diff --git a/tests/core/pyspec/eth2spec/test/helpers/constants.py b/tests/core/pyspec/eth2spec/test/helpers/constants.py
index 757f1c007..76c3de9d6 100644
--- a/tests/core/pyspec/eth2spec/test/helpers/constants.py
+++ b/tests/core/pyspec/eth2spec/test/helpers/constants.py
@@ -27,18 +27,21 @@ WHISK = SpecForkName('whisk')
 MAINNET_FORKS = (PHASE0, ALTAIR, BELLATRIX, CAPELLA)
 LATEST_FORK = MAINNET_FORKS[-1]
 # The forks that pytest can run with.
+# Note: when adding a new fork here, all tests from previous forks with decorator `with_X_and_later`
+#       will run on the new fork. To skip this behaviour, add the fork to `ALLOWED_TEST_RUNNER_FORKS`
 ALL_PHASES = (
     # Formal forks
     *MAINNET_FORKS,
     DENEB,
     # Experimental patches
     EIP6110,
-    WHISK,
 )
 # The forks that have light client specs
 LIGHT_CLIENT_TESTING_FORKS = (*[item for item in MAINNET_FORKS if item != PHASE0], DENEB)
 # The forks that output to the test vectors.
 TESTGEN_FORKS = (*MAINNET_FORKS, DENEB, EIP6110, WHISK)
+# Forks allowed in the test runner `--fork` flag, to fail fast in case of typos
+ALLOWED_TEST_RUNNER_FORKS = (*ALL_PHASES, WHISK)
 
 ALL_FORK_UPGRADES = {
     # pre_fork_name: post_fork_name