--- a/thirdparty/thirdpartyinit.m
+++ b/thirdparty/thirdpartyinit.m
@@ -2,7 +2,12 @@
 
 p=[bp,'thirdparty',filesep];
 
-addpath([p,'PolygonClip']);
+% PolygonClip is not distributed with the Octave-forge package
+s=[p,'PolygonClip'];
+if exist(s)
+    addpath(s);
+end;
+
 addpath([p,'Playrec']);