diff --git a/extensions/fablabchemnitz/apply_transformations/apply_transformations.py b/extensions/fablabchemnitz/apply_transformations/apply_transformations.py
index 5dc96e91..a9f6cf49 100644
--- a/extensions/fablabchemnitz/apply_transformations/apply_transformations.py
+++ b/extensions/fablabchemnitz/apply_transformations/apply_transformations.py
@@ -46,7 +46,8 @@ class ApplyTransformations(inkex.EffectExtension):
                 try:
                     #stroke_width = float(style.get('stroke-width').strip().replace("px", ""))
                     stroke_width = self.svg.uutounit(style.get('stroke-width').strip())
-                    stroke_width *= math.sqrt(abs(transf.a * transf.d))
+                    #stroke_width *= math.sqrt(abs(transf.a * transf.d))
+                    stroke_width *= math.sqrt(abs(transf.a * transf.d - transf.b * transf.c))
                     style['stroke-width'] = str(stroke_width)
                     update = True
                 except AttributeError: