diff --git a/history.txt b/history.txt
index 202682e..bcc8a0a 100644
--- a/history.txt
+++ b/history.txt
@@ -1,3 +1,5 @@
+* If the pipe diameter is not specified, the dent depth as a percentage of the diameter is 0.
+
 27.08.2026 ver.1.27
 -------------------
 
diff --git a/pipeline_csv/csvfile/defect.py b/pipeline_csv/csvfile/defect.py
index 6a06d5b..116c6da 100644
--- a/pipeline_csv/csvfile/defect.py
+++ b/pipeline_csv/csvfile/defect.py
@@ -85,6 +85,8 @@ def depth_percent(self):
 
         # Depth.HundredthsOfMillimeter
         if self.is_dent:
+            if self.pipe.diameter is None:
+                return 0
             return float(self.row.depth_max) / float(self.pipe.diameter)
 
         return float(self.row.depth_max) / (self.pipe.thick / 10.0)
diff --git a/tests/test/test_csv/test_defect.py b/tests/test/test_csv/test_defect.py
index e5bcb9f..6a9feb4 100644
--- a/tests/test/test_csv/test_defect.py
+++ b/tests/test/test_csv/test_defect.py
@@ -89,6 +89,9 @@ def test_depth(self):  # pylint: disable=too-many-statements
         assert mloss_defekt.depth_percent is None
         assert mloss_defekt.depth_mm is None
 
+        dent_defekt.pipe.diameter = None
+        assert dent_defekt.depth_percent == 0
+
     def test_props(self):  # pylint: disable=too-many-statements
         """Check defekt properties."""
         from pipeline_csv import TypeHorWeld