diff --git a/lib/run_tests.py b/lib/run_tests.py
index 1b4baa5..7457cd7 100644
--- a/lib/run_tests.py
+++ b/lib/run_tests.py
@@ -42,10 +42,15 @@ class TestRunner:
     def find_test_files(self):
         """Find DXF files in testdata directory - all files or specific file"""
         if self.target_file:
+            # Remove .dxf suffix if present to avoid double extension
+            clean_target = self.target_file
+            if clean_target.endswith('.dxf'):
+                clean_target = clean_target[:-4]
+
             # Check if specific file exists
-            target_dxf = self.testdata_dir / f"{self.target_file}.dxf"
+            target_dxf = self.testdata_dir / f"{clean_target}.dxf"
             if target_dxf.exists():
-                return [self.target_file]
+                return [clean_target]
             else:
                 print(f"Error: Test file {target_dxf} not found")
                 return []