diff --git a/history.txt b/history.txt
index fa1d628..8d7379a 100644
--- a/history.txt
+++ b/history.txt
@@ -1,3 +1,5 @@
+- Fix error on depth percent calculation for dent with Depth.PercentWallThickness.
+
 19.06.2026 ver.1.26
 -------------------
 
diff --git a/pipeline_csv/csvfile/defect.py b/pipeline_csv/csvfile/defect.py
index cb7124b..6a06d5b 100644
--- a/pipeline_csv/csvfile/defect.py
+++ b/pipeline_csv/csvfile/defect.py
@@ -85,7 +85,7 @@ def depth_percent(self):
 
         # Depth.HundredthsOfMillimeter
         if self.is_dent:
-            return float(self.row.depth_max) / self.pipe.diameter
+            return float(self.row.depth_max) / float(self.pipe.diameter)
 
         return float(self.row.depth_max) / (self.pipe.thick / 10.0)