Index: trunk/src/org/openstreetmap/josm/tools/Geometry.java
===================================================================
--- trunk/src/org/openstreetmap/josm/tools/Geometry.java	(revision 11660)
+++ trunk/src/org/openstreetmap/josm/tools/Geometry.java	(revision 11664)
@@ -345,6 +345,4 @@
         CheckParameterUtil.ensureValidCoordinates(p3, "p3");
         CheckParameterUtil.ensureValidCoordinates(p4, "p4");
-
-        if (!p1.isValid()) throw new IllegalArgumentException(p1+" is invalid");
 
         // Basically, the formula from wikipedia is used: