diff --git a/clause/set.go b/clause/set.go
index 2971f421..5c281d96 100644
--- a/clause/set.go
+++ b/clause/set.go
@@ -1,6 +1,8 @@
 package clause
 
-import "sort"
+import (
+	"sort"
+)
 
 type Set []Assignment
 
@@ -28,7 +30,9 @@ func (set Set) Build(builder Builder) {
 		}
 	} else {
 		builder.WriteQuoted(Column{Name: PrimaryKey})
+		builder.WriteByte(' ')
 		builder.WriteByte('=')
+		builder.WriteByte(' ')
 		builder.WriteQuoted(Column{Name: PrimaryKey})
 	}
 }
diff --git a/clause/set_test.go b/clause/set_test.go
index 8e97ac6f..8232c3e8 100644
--- a/clause/set_test.go
+++ b/clause/set_test.go
@@ -35,7 +35,6 @@ func TestSet(t *testing.T) {
 		{
 			[]clause.Interface{
 				clause.Update{},
-				clause.Set([]clause.Assignment{{clause.PrimaryColumn, 1}}),
 				clause.Set([]clause.Assignment{
 					{clause.Column{Name: "name"}, "jinzhu"},
 					{clause.Column{Name: "age"}, 18},