diff --git a/libs/ardour/rb_effect.cc b/libs/ardour/rb_effect.cc
index 23ffa94460..70053a3225 100644
--- a/libs/ardour/rb_effect.cc
+++ b/libs/ardour/rb_effect.cc
@@ -302,7 +302,7 @@ RBEffect::run (boost::shared_ptr<Region> r, Progress* progress)
 			}
 		}
 
-		while ((avail = stretcher.available()) >= 0) {
+		while ((avail = stretcher.available()) > 0) {
 
 			samplecnt_t this_read = min (bufsize, avail);