diff --git a/async_producer.go b/async_producer.go
index 8e229490f8..92f9f53fd3 100644
--- a/async_producer.go
+++ b/async_producer.go
@@ -103,6 +103,7 @@ type flagSet int8
 const (
 	chaser   flagSet = 1 << iota // message is last in a group that failed
 	shutdown                     // start the shutdown process
+	returned                     // returned mid-processing, so skip it (hacky fix for #449)
 )
 
 // ProducerMessage is the collection of elements passed to the Producer in order to send a message.
@@ -662,12 +663,12 @@ func (f *flusher) run() {
 func (f *flusher) groupAndFilter(batch []*ProducerMessage) map[string]map[int32][]*ProducerMessage {
 	msgSets := make(map[string]map[int32][]*ProducerMessage)
 
-	for i, msg := range batch {
+	for _, msg := range batch {
 
 		if f.currentRetries[msg.Topic] != nil && f.currentRetries[msg.Topic][msg.Partition] != nil {
 			// we're currently retrying this partition so we need to filter out this message
 			f.parent.retryMessages([]*ProducerMessage{msg}, f.currentRetries[msg.Topic][msg.Partition])
-			batch[i] = nil
+			msg.flags |= returned
 
 			if msg.flags&chaser == chaser {
 				// ...but now we can start processing future messages again
@@ -791,12 +792,14 @@ func (p *asyncProducer) buildRequest(batch map[string]map[int32][]*ProducerMessa
 				if msg.Key != nil {
 					if keyBytes, err = msg.Key.Encode(); err != nil {
 						p.returnError(msg, err)
+						msg.flags |= returned
 						continue
 					}
 				}
 				if msg.Value != nil {
 					if valBytes, err = msg.Value.Encode(); err != nil {
 						p.returnError(msg, err)
+						msg.flags |= returned
 						continue
 					}
 				}
@@ -851,7 +854,7 @@ func (p *asyncProducer) returnError(msg *ProducerMessage, err error) {
 
 func (p *asyncProducer) returnErrors(batch []*ProducerMessage, err error) {
 	for _, msg := range batch {
-		if msg != nil {
+		if msg.flags&returned == 0 {
 			p.returnError(msg, err)
 		}
 	}
@@ -859,7 +862,7 @@ func (p *asyncProducer) returnErrors(batch []*ProducerMessage, err error) {
 
 func (p *asyncProducer) returnSuccesses(batch []*ProducerMessage) {
 	for _, msg := range batch {
-		if msg == nil {
+		if msg.flags&returned == returned {
 			continue
 		}
 		if p.conf.Producer.Return.Successes {