diff --git a/bindings/python/src/Conversions.hh b/bindings/python/src/Conversions.hh
index c6dd323543a..ae2059ab708 100644
--- a/bindings/python/src/Conversions.hh
+++ b/bindings/python/src/Conversions.hh
@@ -241,7 +241,7 @@ namespace PyXRootD
   {
       static PyObject* Convert( XrdCl::Buffer *buffer )
       {
-        return Py_BuildValue( "s#", buffer->GetBuffer(), buffer->GetSize() );
+        return Py_BuildValue( "y#", buffer->GetBuffer(), buffer->GetSize() );
       }
   };
 
@@ -249,7 +249,7 @@ namespace PyXRootD
   {
       static PyObject* Convert( XrdCl::ChunkInfo *chunk )
       {
-        PyObject *o = Py_BuildValue( "s#", chunk->buffer, chunk->length );
+        PyObject *o = Py_BuildValue( "y#", chunk->buffer, chunk->length );
         delete[] (char*) chunk->buffer;
         return o;
       }
@@ -267,7 +267,7 @@ namespace PyXRootD
         for ( uint32_t i = 0; i < chunks.size(); ++i ) {
           XrdCl::ChunkInfo chunk = chunks.at( i );
 
-          PyObject *buffer = Py_BuildValue( "s#", (const char *) chunk.buffer,
+          PyObject *buffer = Py_BuildValue( "y#", (const char *) chunk.buffer,
                                                   chunk.length );
           PyList_SET_ITEM( pychunks, i,
               Py_BuildValue( "{sOsOsO}",
diff --git a/bindings/python/src/PyXRootDFile.cc b/bindings/python/src/PyXRootDFile.cc
index 889a048495f..4f5ecc4cba3 100644
--- a/bindings/python/src/PyXRootDFile.cc
+++ b/bindings/python/src/PyXRootDFile.cc
@@ -195,7 +195,7 @@ namespace PyXRootD
     else {
       uint32_t bytesRead;
       async( status = self->file->Read( offset, size, buffer, bytesRead, timeout ) );
-      pyresponse = Py_BuildValue( "s#", buffer, bytesRead );
+      pyresponse = Py_BuildValue( "y#", buffer, bytesRead );
       delete[] buffer;
     }