diff --git a/pageserver/src/config.rs b/pageserver/src/config.rs
index 9e341230cf..88a7f15b21 100644
--- a/pageserver/src/config.rs
+++ b/pageserver/src/config.rs
@@ -797,7 +797,8 @@ impl PageServerConf {
             )?);
         }
         if let Some(max_lsn_wal_lag) = item.get("max_lsn_wal_lag") {
-            t_conf.max_lsn_wal_lag = Some(parse_toml_from_str("max_lsn_wal_lag", max_lsn_wal_lag)?);
+            t_conf.max_lsn_wal_lag =
+                Some(deserialize_from_item("max_lsn_wal_lag", max_lsn_wal_lag)?);
         }
         if let Some(trace_read_requests) = item.get("trace_read_requests") {
             t_conf.trace_read_requests =
diff --git a/test_runner/regress/test_tenant_conf.py b/test_runner/regress/test_tenant_conf.py
index 8677a554f7..dc523364dc 100644
--- a/test_runner/regress/test_tenant_conf.py
+++ b/test_runner/regress/test_tenant_conf.py
@@ -151,6 +151,7 @@ eviction_policy = { "kind" = "LayerAccessThreshold", period = "20s", threshold =
         "eviction_policy": json.dumps(
             {"kind": "LayerAccessThreshold", "period": "80s", "threshold": "42h"}
         ),
+        "max_lsn_wal_lag": "13000000",
     }
     env.neon_cli.config_tenant(
         tenant_id=tenant,
@@ -206,6 +207,7 @@ eviction_policy = { "kind" = "LayerAccessThreshold", period = "20s", threshold =
     assert updated_effective_config["gc_horizon"] == 67108864
     assert updated_effective_config["image_creation_threshold"] == 2
     assert updated_effective_config["pitr_interval"] == "7days"
+    assert updated_effective_config["max_lsn_wal_lag"] == 13000000
 
     # restart the pageserver and ensure that the config is still correct
     env.pageserver.stop()
@@ -265,6 +267,7 @@ eviction_policy = { "kind" = "LayerAccessThreshold", period = "20s", threshold =
         "period": "20s",
         "threshold": "23h",
     }
+    assert final_effective_config["max_lsn_wal_lag"] == 10 * 1024 * 1024
 
     # restart the pageserver and ensure that the config is still correct
     env.pageserver.stop()