diff --git a/async_postgres/pg_advisory_lock.nim b/async_postgres/pg_advisory_lock.nim
index d7ef202..146b0cd 100644
--- a/async_postgres/pg_advisory_lock.nim
+++ b/async_postgres/pg_advisory_lock.nim
@@ -56,7 +56,7 @@
 
 import std/[macros, importutils]
 
-import async_backend, pg_types, pg_connection, pg_client
+import async_backend, pg_protocol, pg_types, pg_connection, pg_client
 
 privateAccess(PgConnection)
 
@@ -89,14 +89,26 @@ template unlockSessionLock(
     dec conn.heldSessionLocks
   released
 
+proc ensureXactScope(conn: PgConnection) {.inline.} =
+  # In tsIdle the acquire's implicit tx would commit and drop the lock before
+  # body runs, silently losing mutual exclusion.
+  if conn.txStatus != tsInTransaction:
+    raise newException(
+      PgStateError,
+      "transaction-level advisory lock requires an active transaction " & "(txStatus: " &
+        $conn.txStatus & "); wrap the call in withTransaction",
+    )
+
 template acquireXactLock(
     conn: PgConnection, sql: string, params: seq[PgParam], t: Duration
 ) =
+  ensureXactScope(conn)
   discard await conn.queryValue(sql, params, timeout = t)
 
 template tryXactLock(
     conn: PgConnection, sql: string, params: seq[PgParam], t: Duration
 ): bool =
+  ensureXactScope(conn)
   await conn.queryValue(bool, sql, params, timeout = t)
 
 # Session-level exclusive locks
diff --git a/tests/test_advisory_lock.nim b/tests/test_advisory_lock.nim
index 9885d6c..af53904 100644
--- a/tests/test_advisory_lock.nim
+++ b/tests/test_advisory_lock.nim
@@ -166,6 +166,30 @@ suite "Advisory Lock: transaction-level (int64)":
 
     waitFor t()
 
+  test "xact lock outside transaction raises PgStateError":
+    proc t() {.async.} =
+      let conn = await connect(plainConfig())
+      defer:
+        await conn.close()
+      doAssertRaises(PgStateError):
+        waitFor conn.advisoryLockXact(40010'i64)
+      doAssertRaises(PgStateError):
+        waitFor conn.advisoryLockXactShared(40011'i64)
+      doAssertRaises(PgStateError):
+        discard waitFor conn.advisoryTryLockXact(40012'i64)
+      doAssertRaises(PgStateError):
+        discard waitFor conn.advisoryTryLockXactShared(40013'i64)
+      doAssertRaises(PgStateError):
+        waitFor conn.advisoryLockXact(1'i32, 2'i32)
+      doAssertRaises(PgStateError):
+        waitFor conn.advisoryLockXactShared(3'i32, 4'i32)
+      doAssertRaises(PgStateError):
+        discard waitFor conn.advisoryTryLockXact(5'i32, 6'i32)
+      doAssertRaises(PgStateError):
+        discard waitFor conn.advisoryTryLockXactShared(7'i32, 8'i32)
+
+    waitFor t()
+
 suite "Advisory Lock: two-key (int32, int32)":
   test "lock and unlock":
     proc t() {.async.} =
@@ -228,8 +252,9 @@ suite "Advisory Lock: two-key (int32, int32)":
         await conn2.close()
       conn1.withTransaction:
         await conn1.advisoryLockXactShared(9'i32, 10'i32)
-        let acquired = await conn2.advisoryTryLockXactShared(9'i32, 10'i32)
+        let acquired = await conn2.advisoryTryLockShared(9'i32, 10'i32)
         doAssert acquired
+        discard await conn2.advisoryUnlockShared(9'i32, 10'i32)
 
     waitFor t()
 
@@ -392,8 +417,9 @@ suite "Advisory Lock: withAdvisoryLockXact template":
         await conn2.close()
       conn1.withTransaction:
         conn1.withAdvisoryLockXactShared(17'i32, 18'i32):
-          let acquired = await conn2.advisoryTryLockXactShared(17'i32, 18'i32)
+          let acquired = await conn2.advisoryTryLockShared(17'i32, 18'i32)
           doAssert acquired
+          discard await conn2.advisoryUnlockShared(17'i32, 18'i32)
 
     waitFor t()