diff --git a/libs/ardour/internal_send.cc b/libs/ardour/internal_send.cc
index fcf8635f72..d8bc1ccd98 100644
--- a/libs/ardour/internal_send.cc
+++ b/libs/ardour/internal_send.cc
@@ -113,11 +113,10 @@ InternalSend::run (BufferSet& bufs, framepos_t start_frame, framepos_t end_frame
 	// we have to copy the input, because we may alter the buffers with the amp
 	// in-place, which a send must never do.
 
-	assert(mixbufs.available() >= bufs.count());
-
 	if (_panshell && !_panshell->bypassed()) {
 		_panshell->run (bufs, mixbufs, start_frame, end_frame, nframes);
 	} else {
+		assert (mixbufs.available() >= bufs.count());
 		mixbufs.read_from (bufs, nframes);
 	}