diff --git a/expression/builtin_time_test.go b/expression/builtin_time_test.go
index c9b03ba0618e6..7d4f44301c06a 100644
--- a/expression/builtin_time_test.go
+++ b/expression/builtin_time_test.go
@@ -1591,6 +1591,7 @@ func (s *testEvaluatorSuite) TestTimeDiff(c *C) {
 		{[]interface{}{"10:10:10", "10:9:0"}, "00:01:10", false, 0, false},
 		{[]interface{}{"2016-12-00 12:00:00", "10:9:0"}, "", true, 0, false},
 		{[]interface{}{"2016-12-00 12:00:00", ""}, "", true, 0, true},
+		{[]interface{}{"00:00:00.000000", "00:00:00.000001"}, "-00:00:00.000001", false, 6, false},
 	}
 
 	for _, t := range tests {
diff --git a/types/convert.go b/types/convert.go
index ee32a73a30f1d..0239517431525 100644
--- a/types/convert.go
+++ b/types/convert.go
@@ -314,6 +314,9 @@ func StrToDuration(sc *stmtctx.StatementContext, str string, fsp int8) (d Durati
 	if length > 0 && str[0] == '-' {
 		length--
 	}
+	if n := strings.IndexByte(str, '.'); n >= 0 {
+		length = length - len(str[n:])
+	}
 	// Timestamp format is 'YYYYMMDDHHMMSS' or 'YYMMDDHHMMSS', which length is 12.
 	// See #3923, it explains what we do here.
 	if length >= 12 {
diff --git a/types/convert_test.go b/types/convert_test.go
index 34a5f5aea5435..cab7670b64104 100644
--- a/types/convert_test.go
+++ b/types/convert_test.go
@@ -1124,6 +1124,8 @@ func (s *testTypeConvertSuite) TestStrToDuration(c *C) {
 		{"20190101180000", 6, false},
 		{"20190101180000", 1, false},
 		{"20190101181234", 3, false},
+		{"00:00:00.000000", 6, true},
+		{"00:00:00", 0, true},
 	}
 	for _, tt := range tests {
 		_, _, isDuration, err := StrToDuration(sc, tt.str, tt.fsp)