diff --git a/tests/org.eclipse.qvtd.xtext.qvtcore.tests/models/hsv2hsl/HSV2HSL.qvtc b/tests/org.eclipse.qvtd.xtext.qvtcore.tests/models/hsv2hsl/HSV2HSL.qvtc
index f9ff82b..d8f5fbc 100644
--- a/tests/org.eclipse.qvtd.xtext.qvtcore.tests/models/hsv2hsl/HSV2HSL.qvtc
+++ b/tests/org.eclipse.qvtd.xtext.qvtcore.tests/models/hsv2hsl/HSV2HSL.qvtc
@@ -94,10 +94,13 @@
 
 query hsv2hsl::hsv2rgb(color : HSVTree::HSV[1]) : HSV2HSL::RGB[1]
 {
-	let hsv : Sequence(String) = color.tokenize(',') in
-	let h : Integer = hsv->at(1).toReal().round() in
-	let s : Real = hsv->at(2).toReal()/100.0 in
-	let v : Real = hsv->at(3).toReal()/100.0 in
+	let hsv : Sequence(String[*|1]) = color.tokenize(',') in
+	let hopt : Real = hsv->at(1).toReal() in
+	let sopt : Real = hsv->at(2).toReal() in
+	let vopt : Real = hsv->at(3).toReal() in
+	let h : Integer = if hopt <> null then hopt.round() else 0 endif in
+	let s : Real = if sopt <> null then sopt/100.0 else 0 endif in
+	let v : Real = if vopt <> null then vopt/100.0 else 0 endif in
 	let c : Real = v * s in
 	let hh1 : Real = h/120 in
 	let hh2 : Real = 2 * (hh1 - hh1.floor()) in
@@ -118,10 +121,13 @@
 
 query hsv2hsl::rgb2hsl(color : HSV2HSL::RGB[1]) : HSLTree::HSL[1]
 {
-	let rgb : Sequence(String) = color.tokenize(',') in
-	let r : Real = rgb->at(1).toReal()/255.0 in
-	let g : Real = rgb->at(2).toReal()/255.0 in
-	let b : Real = rgb->at(3).toReal()/255.0 in
+	let rgb : Sequence(String[*|1]) = color.tokenize(',') in
+	let ropt : Real = rgb->at(1).toReal() in
+	let gopt : Real = rgb->at(2).toReal() in
+	let bopt : Real = rgb->at(3).toReal() in
+	let r : Real = if ropt <> null then ropt/255.0 else 0 endif in
+	let g : Real = if gopt <> null then gopt/255.0 else 0 endif in
+	let b : Real = if bopt <> null then bopt/255.0 else 0 endif in
 	let cMax : Real = r.max(g).max(b) in
 	let cMin : Real = r.min(g).min(b) in
 	let l : Real = (cMax + cMin) / 2 in