diff --git a/lib/logstorage/pipe_sort_test.go b/lib/logstorage/pipe_sort_test.go
index 65accb0d6..dab5c12f7 100644
--- a/lib/logstorage/pipe_sort_test.go
+++ b/lib/logstorage/pipe_sort_test.go
@@ -129,6 +129,7 @@ func TestPipeSort(t *testing.T) {
 		{
 			{"_msg", `def`},
 			{"a", `1`},
+			{"b", ""},
 		},
 	})
 
diff --git a/lib/logstorage/pipe_unpack_json_test.go b/lib/logstorage/pipe_unpack_json_test.go
index a889a1fde..52a12d00f 100644
--- a/lib/logstorage/pipe_unpack_json_test.go
+++ b/lib/logstorage/pipe_unpack_json_test.go
@@ -216,6 +216,7 @@ func expectPipeResults(t *testing.T, pipeStr string, rows, rowsExpected [][]Fiel
 		brw.writeRow(row)
 	}
 	brw.flush()
+	pp.flush()
 
 	ppTest.expectRows(t, rowsExpected)
 }
@@ -272,7 +273,6 @@ func (brw *testBlockResultWriter) flush() {
 	for i := range brw.rcs {
 		brw.rcs[i].resetValues()
 	}
-	brw.ppBase.flush()
 }
 
 func newTestPipeProcessor() *testPipeProcessor {