diff --git a/clause/limit.go b/clause/limit.go
index 2082f4d9..184f6025 100644
--- a/clause/limit.go
+++ b/clause/limit.go
@@ -21,7 +21,7 @@ func (limit Limit) Build(builder Builder) {
 	}
 	if limit.Offset > 0 {
 		if limit.Limit > 0 {
-			builder.WriteString(" ")
+			builder.WriteByte(' ')
 		}
 		builder.WriteString("OFFSET ")
 		builder.WriteString(strconv.Itoa(limit.Offset))
diff --git a/clause/where.go b/clause/where.go
index 10b6df85..a29401cf 100644
--- a/clause/where.go
+++ b/clause/where.go
@@ -72,9 +72,9 @@ func buildExprs(exprs []Expression, builder Builder, joinCond string) {
 		}
 
 		if wrapInParentheses {
-			builder.WriteString(`(`)
+			builder.WriteByte('(')
 			expr.Build(builder)
-			builder.WriteString(`)`)
+			builder.WriteByte(')')
 			wrapInParentheses = false
 		} else {
 			expr.Build(builder)
diff --git a/statement.go b/statement.go
index cb471776..abf646b8 100644
--- a/statement.go
+++ b/statement.go
@@ -130,7 +130,7 @@ func (stmt *Statement) QuoteTo(writer clause.Writer, field interface{}) {
 		writer.WriteByte('(')
 		for idx, d := range v {
 			if idx > 0 {
-				writer.WriteString(",")
+				writer.WriteByte(',')
 			}
 			stmt.QuoteTo(writer, d)
 		}
@@ -143,7 +143,7 @@ func (stmt *Statement) QuoteTo(writer clause.Writer, field interface{}) {
 		writer.WriteByte('(')
 		for idx, d := range v {
 			if idx > 0 {
-				writer.WriteString(",")
+				writer.WriteByte(',')
 			}
 			stmt.DB.Dialector.QuoteTo(writer, d)
 		}
diff --git a/utils/tests/dummy_dialecter.go b/utils/tests/dummy_dialecter.go
index 9543f750..2990c20f 100644
--- a/utils/tests/dummy_dialecter.go
+++ b/utils/tests/dummy_dialecter.go
@@ -49,7 +49,7 @@ func (DummyDialector) QuoteTo(writer clause.Writer, str string) {
 				shiftDelimiter = 0
 				underQuoted = false
 				continuousBacktick = 0
-				writer.WriteString("`")
+				writer.WriteByte('`')
 			}
 			writer.WriteByte(v)
 			continue
@@ -74,7 +74,7 @@ func (DummyDialector) QuoteTo(writer clause.Writer, str string) {
 	if continuousBacktick > 0 && !selfQuoted {
 		writer.WriteString("``")
 	}
-	writer.WriteString("`")
+	writer.WriteByte('`')
 }
 
 func (DummyDialector) Explain(sql string, vars ...interface{}) string {