diff --git a/pkg/keyvisual/matrix/axis.go b/pkg/keyvisual/matrix/axis.go
index 4f5f134fa7..379ea97fc7 100644
--- a/pkg/keyvisual/matrix/axis.go
+++ b/pkg/keyvisual/matrix/axis.go
@@ -182,7 +182,7 @@ func (c *chunk) Reduce(newKeys []string) chunk {
 	endKeys := newKeys[1:]
 	j := 0
 	for i, value := range c.Values {
-		if equal(keys[i], endKeys[j]) {
+		if i > 0 && equal(keys[i], endKeys[j]) {
 			j++
 		}
 		newValues[j] += value
diff --git a/pkg/keyvisual/matrix/axis_test.go b/pkg/keyvisual/matrix/axis_test.go
index b4dfc4714f..ae3e994516 100644
--- a/pkg/keyvisual/matrix/axis_test.go
+++ b/pkg/keyvisual/matrix/axis_test.go
@@ -20,3 +20,31 @@ import (
 var _ = Suite(&testAxisSuite{})
 
 type testAxisSuite struct{}
+
+func (s *testAxisSuite) TestChunkReduce(c *C) {
+	testcases := []struct {
+		keys      []string
+		values    []uint64
+		newKeys   []string
+		newValues []uint64
+	}{
+		{
+			[]string{"", "a", "b", "c", ""},
+			[]uint64{1, 10, 100, 1000},
+			[]string{"", "b", ""},
+			[]uint64{11, 1100},
+		},
+		{
+			[]string{"", "a", "b", "c", ""},
+			[]uint64{1, 10, 100, 1000},
+			[]string{"", ""},
+			[]uint64{1111},
+		},
+	}
+
+	for _, testcase := range testcases {
+		originChunk := createChunk(testcase.keys, testcase.values)
+		reduceChunk := originChunk.Reduce(testcase.newKeys)
+		c.Assert(reduceChunk.Values, DeepEquals, testcase.newValues)
+	}
+}
diff --git a/release-version b/release-version
index 1bf7f6b34e..3809da7b70 100644
--- a/release-version
+++ b/release-version
@@ -1,3 +1,3 @@
 # This file specifies the TiDB Dashboard internal version, which will be printed in `--version`
 # and UI. In release branch, changing this file will result in publishing a new version and tag.
-2020.09.21.1
+2020.10.21.1
diff --git a/ui/dashboardApp/index.ts b/ui/dashboardApp/index.ts
index 251697dff9..cd9bd6fcd9 100644
--- a/ui/dashboardApp/index.ts
+++ b/ui/dashboardApp/index.ts
@@ -56,7 +56,7 @@ async function main() {
   } catch (e) {
     Modal.error({
       title: 'Failed to connect to TiDB Dashboard server',
-      content: e.stack,
+      content: '' + e,
       okText: 'Reload',
       onOk: () => window.location.reload(),
     })