diff --git a/tools/linter_lib/custom_check.py b/tools/linter_lib/custom_check.py
index 7f0faeeedd..3b48a965c3 100644
--- a/tools/linter_lib/custom_check.py
+++ b/tools/linter_lib/custom_check.py
@@ -267,6 +267,12 @@ python_rules = RuleList(
             "good_lines": ["assertEqual(1, 2)"],
             "bad_lines": ["assertEquals(1, 2)"],
         },
+        {
+            "pattern": "assertEqual[(]len[(][^ ]*[)],",
+            "description": "Use the assert_length helper instead of assertEqual(len(..), ..).",
+            "good_lines": ["assert_length(data, 2)"],
+            "bad_lines": ["assertEqual(len(data), 2)"],
+        },
         {
             "pattern": r"#\s*type:\s*ignore(?!\[[^][]+\] +# +\S)",
             "exclude": {"tools/tests", "zerver/lib/test_runner.py", "zerver/tests"},