diff --git a/src/output/plugins/JackOutputPlugin.cxx b/src/output/plugins/JackOutputPlugin.cxx
index 2c13f7845..6b6289eb7 100644
--- a/src/output/plugins/JackOutputPlugin.cxx
+++ b/src/output/plugins/JackOutputPlugin.cxx
@@ -537,7 +537,10 @@ JackOutput::Start()
 		jports = nullptr;
 	}
 
-	AtScopeExit(jports) { free(jports); };
+	AtScopeExit(jports) {
+		if (jports != nullptr)
+			jack_free(jports);
+	};
 
 	assert(num_dports > 0);