diff --git a/libs/pbd/pbd/playback_buffer.h b/libs/pbd/pbd/playback_buffer.h
index ac83c81c7f..932f9224b3 100644
--- a/libs/pbd/pbd/playback_buffer.h
+++ b/libs/pbd/pbd/playback_buffer.h
@@ -164,7 +164,7 @@ public:
 			return read_space() >= cnt;
 		}
 		else if (cnt < 0) {
-			return g_atomic_int_get (&reserved) >= cnt;
+			return g_atomic_int_get (&reserved) >= -cnt;
 		}
 		else {
 			return true;