diff --git a/main/streams/filter.c b/main/streams/filter.c
index 1be5cb1b3e50..fdc5dfc00ad2 100644
--- a/main/streams/filter.c
+++ b/main/streams/filter.c
@@ -506,9 +506,9 @@ PHPAPI zend_result php_stream_filter_flush(php_stream_filter *filter, bool finis
 		/* Dump any newly flushed data to the read buffer */
 		if (stream->readpos > 0) {
 			/* Back the buffer up */
-			memcpy(stream->readbuf, stream->readbuf + stream->readpos, stream->writepos - stream->readpos);
-			stream->readpos = 0;
+			memmove(stream->readbuf, stream->readbuf + stream->readpos, stream->writepos - stream->readpos);
 			stream->writepos -= stream->readpos;
+			stream->readpos = 0;
 		}
 		if (flushed_size > (stream->readbuflen - stream->writepos)) {
 			/* Grow the buffer */