diff --git a/.github/workflows/pytest.yml b/.github/workflows/pytest.yml
index d06c02d..688605f 100644
--- a/.github/workflows/pytest.yml
+++ b/.github/workflows/pytest.yml
@@ -96,7 +96,7 @@ jobs:
       # carries, or a change to them is not exercised until after it merges.
       # Consumers use the action; this repository owns the rules.
       - name: Refuse a skip, and a suite that shrank
-        run: tools/check-test-outcome.py "$RUNNER_TEMP/pytest.log" --min-tests 317
+        run: tools/check-test-outcome.py "$RUNNER_TEMP/pytest.log" --min-tests 318
 
       # The rules earn their place by refusing a log that carries what they
       # name. Both fixtures are written here rather than tracked, and the
diff --git a/parser/nullable.py b/parser/nullable.py
index 41c411c..4a64dd5 100644
--- a/parser/nullable.py
+++ b/parser/nullable.py
@@ -27,8 +27,13 @@
 _PARAM = re.compile(
     r'@param\[[^\]]*\]\s+(?P<names>\w+(?:\s*,\s*\w+)*)\s+(?P<desc>.*?)'
     r'(?=\n\s*\*\s*@|\*/|\Z)', re.S)
-_NULLISH = re.compile(r'may be\s+`?NULL`?|can be\s+`?NULL`?|`?NULL`?\s+is allowed'
-                      r'|or\s+`?NULL`?', re.I)
+# Doxygen marks up a parameter or literal it names — ``NULL``, `NULL`, @p NULL,
+# \p NULL — and every one of those spellings is the same note. Reading only the
+# bare and backticked forms drops the ones an author marked up, and a parameter
+# whose note is unread reaches every binding as one that must be supplied.
+_MARKED_NULL = r'(?:[@\\]p\s+)?`?NULL`?'
+_NULLISH = re.compile(rf'may be\s+{_MARKED_NULL}|can be\s+{_MARKED_NULL}'
+                      rf'|{_MARKED_NULL}\s+is allowed|or\s+{_MARKED_NULL}', re.I)
 
 
 def extract_nullable(meos_root: str | Path) -> dict[str, list[str]]:
diff --git a/tests/test_nullable.py b/tests/test_nullable.py
index 0d37bc4..ee158b0 100644
--- a/tests/test_nullable.py
+++ b/tests/test_nullable.py
@@ -36,6 +36,19 @@
 {
   return NULL;
 }
+
+/**
+ * @brief Interpolate between two geography points
+ * @param[in] p1 First point
+ * @param[in] s Spheroid, may be @p NULL when the sphere is meant
+ * @param[in] tol Tolerance, or \\p NULL for the default
+ */
+int
+interpolate_point4d_spheroid(const POINT4D *p1, const SPHEROID *s,
+  const double *tol)
+{
+  return 0;
+}
 '''
 
 
@@ -57,6 +70,14 @@ def test_extracts_only_may_be_null_params(self):
         # `temp`, `inst`, `interp` carry no NULL note -> not nullable
         self.assertNotIn("temp", nul["temporal_as_mfjson"])
 
+    def test_a_null_note_reads_through_the_markup_around_it(self):
+        # Doxygen marks up the literal it names, and `NULL`, @p NULL and \p NULL
+        # are one note. A parameter whose note goes unread reaches every binding
+        # as one that must be supplied.
+        nul = extract_nullable(self.tmp.name)
+        self.assertEqual(nul["interpolate_point4d_spheroid"], ["s", "tol"])
+        self.assertNotIn("p1", nul["interpolate_point4d_spheroid"])
+
     def test_merge_only_existing_params(self):
         idl = {"functions": [
             {"name": "temporal_as_mfjson",