diff --git a/examples/csbkgmodel.py b/examples/csbkgmodel.py
index 28a97e3..c8f0acd 100644
--- a/examples/csbkgmodel.py
+++ b/examples/csbkgmodel.py
@@ -465,6 +465,10 @@ class csbkgmodel(ctools.cscript):
                 # Compute number of rotation angles to be considered
                 rotangle_pattern = int(events.size() / self.m_n_angles) 
                 
+                # Rotangle pattern must not be zero
+                if rotangle_pattern == 0:
+                    rotangle_pattern += 1
+                
                 # Loop over bins  
                 for i in range(self.m_xbins):
                     for j in range(self.m_ybins):