diff --git a/cylc/flow/config.py b/cylc/flow/config.py
index 4ada6044a28..1f726b1496b 100644
--- a/cylc/flow/config.py
+++ b/cylc/flow/config.py
@@ -1795,6 +1795,7 @@ def generate_triggers(self, lexpression, left_nodes, right, seq,
                 )
 
             if self.xtrigger_mgr is None:
+                # Validation only.
                 XtriggerManager.validate_xtrigger(label, xtrig, self.fdir)
             else:
                 self.xtrigger_mgr.add_trig(label, xtrig, self.fdir)
diff --git a/cylc/flow/subprocpool.py b/cylc/flow/subprocpool.py
index 1ae4b129d9d..8a108380301 100644
--- a/cylc/flow/subprocpool.py
+++ b/cylc/flow/subprocpool.py
@@ -79,9 +79,9 @@ def get_func(mod_name, func_name, src_dir):
         AttributeError, if the function is not found in the module
 
     """
-    if func_name in _XTRIG_FUNCS:
+    if (mod_name, func_name) in _XTRIG_FUNCS:
         # Found and cached already.
-        return _XTRIG_FUNCS[func_name]
+        return _XTRIG_FUNCS[(mod_name, func_name)]
 
     # 1. look in <src-dir>/lib/python.
     sys.path.insert(0, os.path.join(src_dir, 'lib', 'python'))
@@ -94,8 +94,8 @@ def get_func(mod_name, func_name, src_dir):
 
     # Module found and imported, return the named function.
 
-    _XTRIG_FUNCS[func_name] = getattr(mod_by_name, func_name)
-    return _XTRIG_FUNCS[func_name]
+    _XTRIG_FUNCS[(mod_name, func_name)] = getattr(mod_by_name, func_name)
+    return _XTRIG_FUNCS[(mod_name, func_name)]
 
 
 def run_function(func_name, json_args, json_kwargs, src_dir):
diff --git a/cylc/flow/xtriggers/wall_clock.py b/cylc/flow/xtriggers/wall_clock.py
index 9d615da115a..e12a17ce8be 100644
--- a/cylc/flow/xtriggers/wall_clock.py
+++ b/cylc/flow/xtriggers/wall_clock.py
@@ -38,12 +38,11 @@ def validate_config(f_args, f_kwargs, f_signature):
     wall_clock(PT1H)
     wall_clock(offset=PT1H)
 
-    And offset must be a valid ISO 8601 interval.
+    The offset must be a valid ISO 8601 interval.
 
     If f_args used, convert to f_kwargs for clarity.
 
     """
-
     n_args = len(f_args)
     n_kwargs = len(f_kwargs)
 
diff --git a/tests/unit/test_subprocpool.py b/tests/unit/test_subprocpool.py
index c239f41a79c..02ee540fd64 100644
--- a/tests/unit/test_subprocpool.py
+++ b/tests/unit/test_subprocpool.py
@@ -167,20 +167,18 @@ def test_xfunction_cache(self):
             python_dir.mkdir(parents=True)
             amandita_file = python_dir / "amandita.py"
             with amandita_file.open(mode="w") as f:
-                f.write("""amandita = lambda: 'chocolate'""")
+                f.write("""choco = lambda: 'chocolate'""")
                 f.flush()
-            f_name = "amandita"
-            fn = get_func(f_name, f_name, temp_dir)
+            m_name = "amandita"  # module
+            f_name =  "choco"  # function
+            fn = get_func(m_name, f_name, temp_dir)
             result = fn()
             self.assertEqual('chocolate', result)
 
             # is in the cache
-            self.assertTrue('amandita' in _XTRIG_FUNCS)
+            self.assertTrue((m_name, f_name) in _XTRIG_FUNCS)
             # returned from cache
-            self.assertEqual(fn, get_func(f_name, f_name, temp_dir))
-            del _XTRIG_FUNCS['amandita']
-            # is not in the cache
-            self.assertFalse('amandita' in _XTRIG_FUNCS)
+            self.assertEqual(fn, get_func(m_name, f_name, temp_dir))
 
     def test_xfunction_import_error(self):
         """Test for error on importing a xtrigger function.