diff --git a/buf.c b/buf.c
index 0b26ecc7..f9f59b26 100644
--- a/buf.c
+++ b/buf.c
@@ -195,8 +195,16 @@ xmlBufDetach(xmlBufPtr buf) {
     if (buf->error)
         return(NULL);
 
-    ret = buf->content;
+    if ((buf->alloc == XML_BUFFER_ALLOC_IO) &&
+        (buf->content != buf->contentIO)) {
+        ret = xmlStrndup(buf->content, buf->use);
+        xmlFree(buf->contentIO);
+    } else {
+        ret = buf->content;
+    }
+
     buf->content = NULL;
+    buf->contentIO = NULL;
     buf->size = 0;
     buf->use = 0;
     UPDATE_COMPAT(buf);
diff --git a/xmlIO.c b/xmlIO.c
index bbfae9b4..56a183a9 100644
--- a/xmlIO.c
+++ b/xmlIO.c
@@ -1394,7 +1394,7 @@ xmlAllocOutputBuffer(xmlCharEncodingHandlerPtr encoder) {
         xmlFree(ret);
 	return(NULL);
     }
-    xmlBufSetAllocationScheme(ret->buffer, XML_BUFFER_ALLOC_DOUBLEIT);
+    xmlBufSetAllocationScheme(ret->buffer, XML_BUFFER_ALLOC_IO);
 
     ret->encoder = encoder;
     if (encoder != NULL) {