diff --git a/BimServer/src/org/bimserver/geometry/StreamingGeometryGenerator.java b/BimServer/src/org/bimserver/geometry/StreamingGeometryGenerator.java
index f8abdb78b6..9fba5345c8 100644
--- a/BimServer/src/org/bimserver/geometry/StreamingGeometryGenerator.java
+++ b/BimServer/src/org/bimserver/geometry/StreamingGeometryGenerator.java
@@ -715,6 +715,10 @@ private String getRepresentationMapKey(HashMapVirtualObject ifcMappedItem) {
 		key.append(mappingSource.getOid());
 		
 		Set<HashMapVirtualObject> colours = getColours(ifcMappedItem);
+		if(colours == null) {
+			return key.toString();
+		}
+		
 		for(HashMapVirtualObject colour : colours) {
 			key.append("_").append(formatColour(colour));
 		}