diff --git a/datastore/datastore.nim b/datastore/datastore.nim
index 0bab3ad..b89d38f 100644
--- a/datastore/datastore.nim
+++ b/datastore/datastore.nim
@@ -46,7 +46,7 @@ method query*(
 proc contains*(self: Datastore, key: Key): Future[bool] {.async: (raises: [CancelledError]).} =
   return (await self.has(key)) |? false
 
-method modify*(self: Datastore, key: Key, fn: Modify): Future[?!void] {.base, gcsafe, async: (raises: [CancelledError, AsyncLockError]), locks: "unknown".} =
+method modify*(self: Datastore, key: Key, fn: Modify): Future[?!void] {.base, gcsafe, async: (raises: [CancelledError]), locks: "unknown".} =
   ## Concurrently safe way of modifying the value associated with the `key`.
   ##
   ## Same as `modifyGet`, but this takes `fn` that doesn't produce any auxillary value.
@@ -54,7 +54,7 @@ method modify*(self: Datastore, key: Key, fn: Modify): Future[?!void] {.base, gc
 
   raiseAssert("Not implemented!")
 
-method modifyGet*(self: Datastore, key: Key, fn: ModifyGet): Future[?!seq[byte]] {.base, gcsafe, async: (raises: [CancelledError, AsyncLockError]), locks: "unknown".} =
+method modifyGet*(self: Datastore, key: Key, fn: ModifyGet): Future[?!seq[byte]] {.base, gcsafe, async: (raises: [CancelledError]), locks: "unknown".} =
   ## Concurrently safe way of updating value associated with the `key`. Returns auxillary value on
   ## successful update.
   ##
diff --git a/datastore/defaultimpl.nim b/datastore/defaultimpl.nim
index c4ae77b..72cd4b3 100644
--- a/datastore/defaultimpl.nim
+++ b/datastore/defaultimpl.nim
@@ -11,7 +11,7 @@ proc defaultModifyGetImpl*(
   lock: AsyncLock,
   key: Key,
   fn: ModifyGet
-  ): Future[?!seq[byte]] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  ): Future[?!seq[byte]] {.async: (raises: [CancelledError]).} =
   # Default implementation, serializes all modify operations using provided lock
   #
   await lock.acquire()
@@ -45,14 +45,17 @@ proc defaultModifyGetImpl*(
 
     return aux.success
   finally:
-    lock.release()
+    try: 
+      lock.release()
+    except AsyncLockError as err:
+      return failure(err)
 
 proc defaultModifyImpl*(
   self: Datastore,
   lock: AsyncLock,
   key: Key,
   fn: Modify
-  ): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  ): Future[?!void] {.async: (raises: [CancelledError]).} =
   proc wrappedFn(maybeValue: ?seq[byte]): Future[(?seq[byte], seq[byte])] {.async.} =
     let res = await fn(maybeValue)
     let ignoredAux = newSeq[byte]()
diff --git a/datastore/fsds.nim b/datastore/fsds.nim
index a7fdb83..a073b4c 100644
--- a/datastore/fsds.nim
+++ b/datastore/fsds.nim
@@ -221,7 +221,7 @@ method query*(
 method modifyGet*(
   self: FSDatastore,
   key: Key,
-  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError]).} =
   var lock: AsyncLock
   try:
     lock = self.locks.mgetOrPut(key, newAsyncLock())
@@ -233,7 +233,7 @@ method modifyGet*(
 method modify*(
   self: FSDatastore,
   key: Key,
-  fn: Modify): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: Modify): Future[?!void] {.async: (raises: [CancelledError]).} =
   var lock: AsyncLock
 
   try:
diff --git a/datastore/leveldb/leveldbds.nim b/datastore/leveldb/leveldbds.nim
index e438470..fc83764 100644
--- a/datastore/leveldb/leveldbds.nim
+++ b/datastore/leveldb/leveldbds.nim
@@ -125,7 +125,7 @@ method query*(
 method modifyGet*(
   self: LevelDbDatastore,
   key: Key,
-  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError]).} =
   var lock: AsyncLock
   try:
     lock = self.locks.mgetOrPut(key, newAsyncLock())
@@ -137,7 +137,7 @@ method modifyGet*(
 method modify*(
   self: LevelDbDatastore,
   key: Key,
-  fn: Modify): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: Modify): Future[?!void] {.async: (raises: [CancelledError]).} =
   var lock: AsyncLock
   try:
     lock = self.locks.mgetOrPut(key, newAsyncLock())
diff --git a/datastore/mountedds.nim b/datastore/mountedds.nim
index f4de063..cebcc4a 100644
--- a/datastore/mountedds.nim
+++ b/datastore/mountedds.nim
@@ -121,7 +121,7 @@ method put*(
 method modifyGet*(
   self: MountedDatastore,
   key: Key,
-  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError]).} =
 
   without mounted =? self.dispatch(key), error:
     return failure(error)
@@ -131,7 +131,7 @@ method modifyGet*(
 method modify*(
   self: MountedDatastore,
   key: Key,
-  fn: Modify): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: Modify): Future[?!void] {.async: (raises: [CancelledError]).} =
 
   without mounted =? self.dispatch(key), error:
     return failure(error)
diff --git a/datastore/sql/sqliteds.nim b/datastore/sql/sqliteds.nim
index ccd9e92..7e9c9bf 100644
--- a/datastore/sql/sqliteds.nim
+++ b/datastore/sql/sqliteds.nim
@@ -40,7 +40,7 @@ proc newRollbackError(rbErr: ref CatchableError, opErrMsg: string): ref Rollback
 proc newRollbackError(rbErr: ref CatchableError, opErr: ref CatchableError): ref RollbackError =
   return newRollbackError(rbErr, opErr)
 
-method modifyGet*(self: SQLiteDatastore, key: Key, fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError, AsyncLockError]).} =
+method modifyGet*(self: SQLiteDatastore, key: Key, fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError]).} =
   var
     retriesLeft = 100 # allows reasonable concurrency, avoids infinite loop
     aux: seq[byte]
@@ -135,7 +135,7 @@ method modifyGet*(self: SQLiteDatastore, key: Key, fn: ModifyGet): Future[?!seq[
   return success(aux)
 
 
-method modify*(self: SQLiteDatastore, key: Key, fn: Modify): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+method modify*(self: SQLiteDatastore, key: Key, fn: Modify): Future[?!void] {.async: (raises: [CancelledError]).} =
   proc wrappedFn(maybeValue: ?seq[byte]): Future[(?seq[byte], seq[byte])] {.async.} =
     let res = await fn(maybeValue)
     let ignoredAux = newSeq[byte]()
diff --git a/datastore/tieredds.nim b/datastore/tieredds.nim
index 2118320..eaf62be 100644
--- a/datastore/tieredds.nim
+++ b/datastore/tieredds.nim
@@ -133,7 +133,7 @@ method put*(
 method modifyGet*(
   self: TieredDatastore,
   key: Key,
-  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: ModifyGet): Future[?!seq[byte]] {.async: (raises: [CancelledError]).} =
 
   let
     pending = await allFinished(self.stores.mapIt(it.modifyGet(key, fn)))
@@ -154,7 +154,7 @@ method modifyGet*(
 method modify*(
   self: TieredDatastore,
   key: Key,
-  fn: Modify): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+  fn: Modify): Future[?!void] {.async: (raises: [CancelledError]).} =
 
   let
     pending = await allFinished(self.stores.mapIt(it.modify(key, fn)))
diff --git a/datastore/typedds.nim b/datastore/typedds.nim
index 4bf76c2..982016e 100644
--- a/datastore/typedds.nim
+++ b/datastore/typedds.nim
@@ -102,7 +102,7 @@ proc get*[T](self: TypedDatastore, key: Key): Future[?!T] {.async: (raises: [Can
     return failure(error)
   return T.decode(bytes)
 
-proc modify*[T](self: TypedDatastore, key: Key, fn: Modify[T]): Future[?!void] {.async: (raises: [CancelledError, AsyncLockError]).} =
+proc modify*[T](self: TypedDatastore, key: Key, fn: Modify[T]): Future[?!void] {.async: (raises: [CancelledError]).} =
   requireDecoder(T)
   requireEncoder(T)
 
@@ -123,7 +123,7 @@ proc modify*[T](self: TypedDatastore, key: Key, fn: Modify[T]): Future[?!void] {
 
   await self.ds.modify(key, wrappedFn)
 
-proc modifyGet*[T, U](self: TypedDatastore, key: Key, fn: ModifyGet[T, U]): Future[?!U] {.async: (raises: [CancelledError, AsyncLockError]).} =
+proc modifyGet*[T, U](self: TypedDatastore, key: Key, fn: ModifyGet[T, U]): Future[?!U] {.async: (raises: [CancelledError]).} =
   requireDecoder(T)
   requireEncoder(T)
   requireEncoder(U)