diff --git a/error.go b/error.go
new file mode 100644
index 0000000..667fffd
--- /dev/null
+++ b/error.go
@@ -0,0 +1,23 @@
+package redis
+
+import (
+	"fmt"
+)
+
+// Redis nil reply.
+var Nil = errorf("redis: nil")
+
+// Redis transaction failed.
+var TxFailedErr = errorf("redis: transaction failed")
+
+type redisError struct {
+	s string
+}
+
+func errorf(s string, args ...interface{}) redisError {
+	return redisError{s: fmt.Sprintf(s, args...)}
+}
+
+func (err redisError) Error() string {
+	return err.s
+}
diff --git a/parser.go b/parser.go
index 729946d..a1a0f55 100644
--- a/parser.go
+++ b/parser.go
@@ -10,12 +10,6 @@ import (
 
 type multiBulkParser func(rd reader, n int64) (interface{}, error)
 
-// Redis nil reply.
-var Nil = errors.New("redis: nil")
-
-// Redis transaction failed.
-var TxFailedErr = errors.New("redis: transaction failed")
-
 var (
 	errReaderTooSmall   = errors.New("redis: reader is too small")
 	errInvalidReplyType = errors.New("redis: invalid reply type")
@@ -132,7 +126,7 @@ func parseReply(rd reader, p multiBulkParser) (interface{}, error) {
 
 	switch line[0] {
 	case '-':
-		return nil, errors.New(string(line[1:]))
+		return nil, errorf(string(line[1:]))
 	case '+':
 		return string(line[1:]), nil
 	case ':':
diff --git a/redis.go b/redis.go
index 7e96a26..8ebab47 100644
--- a/redis.go
+++ b/redis.go
@@ -65,12 +65,14 @@ func (c *baseClient) init(cn *conn, password string, db int64) error {
 	return nil
 }
 
-func (c *baseClient) freeConn(cn *conn, err error) {
-	if err == Nil || err == TxFailedErr {
-		c.putConn(cn)
-	} else {
-		c.removeConn(cn)
+func (c *baseClient) freeConn(cn *conn, ei error) error {
+	if cn.rd.Buffered() > 0 {
+		return c.connPool.Remove(cn)
 	}
+	if _, ok := ei.(redisError); ok {
+		return c.connPool.Put(cn)
+	}
+	return c.connPool.Remove(cn)
 }
 
 func (c *baseClient) removeConn(cn *conn) {