diff --git a/src/aare/common/diffraction_geometry.py b/src/aare/common/diffraction_geometry.py
index d91e9846..92f29a97 100644
--- a/src/aare/common/diffraction_geometry.py
+++ b/src/aare/common/diffraction_geometry.py
@@ -36,7 +36,7 @@ class DiffractionGeometry(BaseModel):
 
     def resolution_angstrom(self, exp_dtz_mm: float) -> float:
         if exp_dtz_mm <= 0:
-            raise ValueError("Detector distance must be positive")
+            raise ValueError(f"Detector distance must be positive {exp_dtz_mm}")
 
         theta = math.atan(self.detector_radius_mm / exp_dtz_mm)*0.5
         return self.wavelength_angstrom / (2 * math.sin(theta))