diff --git a/makepanda/makepanda.py b/makepanda/makepanda.py
index 6aad710b7d..86c5f47fca 100755
--- a/makepanda/makepanda.py
+++ b/makepanda/makepanda.py
@@ -1196,7 +1196,7 @@ if (sys.platform == "darwin"):
     configprc = configprc.replace("p3openal_audio","p3fmod_audio")
     
     # Because <auto> doesn't work well yet.
-    configprc = configprc += "\nplugin-path $THIS_PRC_DIR/../lib"
+    configprc += "\nplugin-path $THIS_PRC_DIR/../lib"
 
 ConditionalWriteFile(GetOutputDir()+"/etc/Config.prc", configprc)
 ConditionalWriteFile(GetOutputDir()+"/etc/Confauto.prc", confautoprc)