diff --git a/structuralcodes/sections/_generic.py b/structuralcodes/sections/_generic.py
index 1e02035e..c5f3c09d 100644
--- a/structuralcodes/sections/_generic.py
+++ b/structuralcodes/sections/_generic.py
@@ -150,8 +150,8 @@ def _calculate_gross_section_properties(self) -> s_res.SectionProperties:
             warnings.warn(
                 'Perimiter computation for a multi polygon is not defined.'
             )
-
-        gp.perimeter = polygon.exterior.length
+        else:
+            gp.perimeter = polygon.exterior.length
 
         # Computation of area: this is taken directly from shapely
         gp.area = self.section.geometry.area