diff --git a/pageserver/src/config.rs b/pageserver/src/config.rs
index 12e2cd99d9..b2ac27b56d 100644
--- a/pageserver/src/config.rs
+++ b/pageserver/src/config.rs
@@ -625,7 +625,7 @@ impl PageServerConf {
     pub fn dummy_conf(repo_dir: Utf8PathBuf) -> Self {
         let pg_distrib_dir = Utf8PathBuf::from(env!("CARGO_MANIFEST_DIR")).join("../pg_install");
 
-        let config_toml = pageserver_api::config::ConfigToml {
+        let mut config_toml = pageserver_api::config::ConfigToml {
             wait_lsn_timeout: Duration::from_secs(60),
             wal_redo_timeout: Duration::from_secs(60),
             pg_distrib_dir: Some(pg_distrib_dir),
@@ -637,6 +637,15 @@ impl PageServerConf {
             control_plane_api: Some(Url::parse("http://localhost:6666").unwrap()),
             ..Default::default()
         };
+
+        // Test authors tend to forget about the default 10min initial lease deadline
+        // when writing tests, which turns their immediate gc requests via mgmt API
+        // into no-ops. Override the binary default here, such that there is no initial
+        // lease deadline by default in tests. Tests that care can always override it
+        // themselves.
+        // Cf https://databricks.atlassian.net/browse/LKB-92?focusedCommentId=6722329
+        config_toml.tenant_config.lsn_lease_length = Duration::from_secs(0);
+
         PageServerConf::parse_and_validate(NodeId(0), config_toml, &repo_dir).unwrap()
     }
 }
diff --git a/test_runner/fixtures/neon_fixtures.py b/test_runner/fixtures/neon_fixtures.py
index 2031ec132e..60a88e1053 100644
--- a/test_runner/fixtures/neon_fixtures.py
+++ b/test_runner/fixtures/neon_fixtures.py
@@ -1315,6 +1315,14 @@ class NeonEnv:
             # This feature is pending rollout.
             # tenant_config["rel_size_v2_enabled"] = True
 
+            # Test authors tend to forget about the default 10min initial lease deadline
+            # when writing tests, which turns their immediate gc requests via mgmt API
+            # into no-ops. Override the binary default here, such that there is no initial
+            # lease deadline by default in tests. Tests that care can always override it
+            # themselves.
+            # Cf https://databricks.atlassian.net/browse/LKB-92?focusedCommentId=6722329
+            tenant_config["lsn_lease_length"] = "0s"
+
             if self.pageserver_remote_storage is not None:
                 ps_cfg["remote_storage"] = remote_storage_to_toml_dict(
                     self.pageserver_remote_storage