diff --git a/festim/exports/derived_quantities/surface_flux.py b/festim/exports/derived_quantities/surface_flux.py
index 511485797..771d3a0e6 100644
--- a/festim/exports/derived_quantities/surface_flux.py
+++ b/festim/exports/derived_quantities/surface_flux.py
@@ -149,7 +149,7 @@ def azimuth_range(self):
     @azimuth_range.setter
     def azimuth_range(self, value):
         if value[0] < 0 or value[1] > 2 * np.pi:
-            raise ValueError("Azimuthal range must be between 0 and pi")
+            raise ValueError("Azimuthal range must be between 0 and 2*pi")
         self._azimuth_range = value
 
     def compute(self):