diff --git a/libs/ardour/audio_unit.cc b/libs/ardour/audio_unit.cc
index c5d70ffe7f..95f41ac400 100644
--- a/libs/ardour/audio_unit.cc
+++ b/libs/ardour/audio_unit.cc
@@ -2899,6 +2899,10 @@ AUPluginInfo::discover_by_description (PluginInfoList& plugs, CAComponentDescrip
 		}
 
 		if (is_blacklisted(CFStringRefToStdString(itemName))) {
+			if (itemName != NULL) {
+				CFRelease(itemName);
+				itemName = NULL;
+			}
 			info << string_compose (_("Skipped blacklisted AU plugin %1 "), CFStringRefToStdString(itemName)) << endmsg;
 			comp = ArdourFindNext (comp, &desc);
 			continue;
diff --git a/libs/ardour/vst3_scan.cc b/libs/ardour/vst3_scan.cc
index 99be890e44..7c67abeeed 100644
--- a/libs/ardour/vst3_scan.cc
+++ b/libs/ardour/vst3_scan.cc
@@ -444,7 +444,15 @@ ARDOUR::vst3_scan_and_cache (std::string const& module_path, std::string const&
 	try {
 		boost::shared_ptr<VST3PluginModule> m = VST3PluginModule::load (module_path);
 		std::vector<VST3Info> nfo;
-		discover_vst3 (m, nfo, verbose);
+		if (!discover_vst3 (m, nfo, verbose)) {
+			delete root;
+			return false;
+		}
+		if (nfo.empty ()) {
+			cerr << "No plugins in VST3 module: '" << module_path << "'\n";
+			delete root;
+			return false;
+		}
 		for (std::vector<VST3Info>::const_iterator i = nfo.begin(); i != nfo.end(); ++i) {
 			cb (module_path, *i);
 			root->add_child_nocopy (i->state ());