diff --git a/gcsfs/core.py b/gcsfs/core.py
index f33f6e8c..2c1afd42 100644
--- a/gcsfs/core.py
+++ b/gcsfs/core.py
@@ -1736,7 +1736,7 @@ def _upload_chunk(self, final=False):
             head = {}
             l = len(data)
 
-            if (l < GCS_MIN_BLOCK_SIZE) and not final:
+            if (l < GCS_MIN_BLOCK_SIZE) and (not final or not self.autocommit):
                 # either flush() was called, but we don't have enough to
                 # push, or we split a big upload, and have less left than one
                 # block.  If this is the final part, OK to violate those
@@ -1818,13 +1818,12 @@ def discard(self):
         """
         if self.location is None:
             return
-        uid = re.findall("upload_id=([^&=?]+)", self.location)
         self.gcsfs.call(
             "DELETE",
-            f"{self.fs._location}/upload/storage/v1/b/{quote(self.bucket)}/o",
-            params={"uploadType": "resumable", "upload_id": uid},
-            json_out=True,
+            self.location,
         )
+        self.location = None
+        self.closed = True
 
     def _simple_upload(self):
         """One-shot upload, less than 5MB"""
diff --git a/gcsfs/retry.py b/gcsfs/retry.py
index 9ae823ba..4bb860ba 100644
--- a/gcsfs/retry.py
+++ b/gcsfs/retry.py
@@ -82,7 +82,8 @@ def validate_response(status, content, path, args=None):
     r: requests response object
     path: associated URL path, for error messages
     """
-    if status >= 400:
+    if status >= 400 and status != 499:
+        # 499 is special "upload was cancelled" status
         if args:
             from .core import quote
 
diff --git a/gcsfs/tests/test_core.py b/gcsfs/tests/test_core.py
index 89dd1760..665106a0 100644
--- a/gcsfs/tests/test_core.py
+++ b/gcsfs/tests/test_core.py
@@ -1424,6 +1424,29 @@ def test_copy_cache_invalidated(gcs):
     assert gcs.isfile(target_file2)
 
 
+def test_transaction(gcs):
+    # https://github.com/fsspec/gcsfs/issues/389
+    if not gcs.on_google:
+        pytest.skip()
+    try:
+        with gcs.transaction:
+            with gcs.open(f"{TEST_BUCKET}/foo", "wb") as f:
+                f.write(b"This is a test string")
+            f.discard()
+            assert not gcs.exists(f"{TEST_BUCKET}/foo")
+            raise ZeroDivisionError
+    except ZeroDivisionError:
+        ...
+    assert not gcs.exists(f"{TEST_BUCKET}/foo")
+
+    with gcs.transaction:
+        with gcs.open(f"{TEST_BUCKET}/foo", "wb") as f:
+            f.write(b"This is a test string")
+        assert not gcs.exists(f"{TEST_BUCKET}/foo")
+
+    assert gcs.cat(f"{TEST_BUCKET}/foo") == b"This is a test string"
+
+
 def test_find_maxdepth(gcs):
     assert gcs.find(f"{TEST_BUCKET}/nested", maxdepth=None) == [
         f"{TEST_BUCKET}/nested/file1",