diff --git a/libs/ardour/plugin_insert.cc b/libs/ardour/plugin_insert.cc
index de6896bb31..48ffb9bf0c 100644
--- a/libs/ardour/plugin_insert.cc
+++ b/libs/ardour/plugin_insert.cc
@@ -413,21 +413,38 @@ PluginInsert::run (BufferSet& bufs, framepos_t /*start_frame*/, framepos_t /*end
 
 	} else {
 
-		/* FIXME: type, audio only */
+		if (is_generator()) {
 
-		uint32_t in = _plugins[0]->get_info()->n_inputs.n_audio();
-		uint32_t out = _plugins[0]->get_info()->n_outputs.n_audio();
+			/* silence all (audio) outputs. Should really declick
+			 * at the transitions of "active"
+			 */
 
-		if (out > in) {
+			uint32_t out = _plugins[0]->get_info()->n_outputs.n_audio();
 
-			/* not active, but something has make up for any channel count increase */
-
-			for (uint32_t n = out - in; n < out; ++n) {
-				memcpy (bufs.get_audio(n).data(), bufs.get_audio(in - 1).data(), sizeof (Sample) * nframes);
+			for (uint32_t n = 0; n < out; ++n) {
+				bufs.get_audio (n).silence (nframes);
 			}
-		}
 
-		bufs.count().set_audio(out);
+			bufs.count().set_audio (out);
+		
+		} else {
+
+			/* does this need to be done with MIDI? it appears not */
+			
+			uint32_t in = _plugins[0]->get_info()->n_inputs.n_audio();
+			uint32_t out = _plugins[0]->get_info()->n_outputs.n_audio();
+			
+			if (out > in) {
+				
+				/* not active, but something has make up for any channel count increase */
+				
+				for (uint32_t n = out - in; n < out; ++n) {
+					memcpy (bufs.get_audio(n).data(), bufs.get_audio(in - 1).data(), sizeof (Sample) * nframes);
+				}
+			}
+			
+			bufs.count().set_audio (out);
+		}
 	}
 
 	_active = _pending_active;