diff --git a/distrho/src/DistrhoPluginAU.cpp b/distrho/src/DistrhoPluginAU.cpp
index 3276c036..4262ca2e 100644
--- a/distrho/src/DistrhoPluginAU.cpp
+++ b/distrho/src/DistrhoPluginAU.cpp
@@ -2038,7 +2038,7 @@ class PluginAU
             case 0x9:
             case 0xD:
                 // unsupported
-                kAudioUnitErr_InvalidPropertyValue;
+                return kAudioUnitErr_InvalidPropertyValue;
             case 0x1:
             case 0x2:
             case 0x3: