diff --git a/mbtrack2/tracking/particles.py b/mbtrack2/tracking/particles.py
index 0d819a81913ccc0d278f2fa102306157374aa048..2b3edbb76dd4546e4f8fce9a2120dd4876b98eb7 100644
--- a/mbtrack2/tracking/particles.py
+++ b/mbtrack2/tracking/particles.py
@@ -288,7 +288,7 @@ class Bunch:
         cov_z = np.cov(self['tau'], self['delta'])
 
         if (np.array(self.ring.optics.local_dispersion)
-                != np.array([0, 0, 0, 0])).all():
+                != np.array([0, 0, 0, 0])).any():
             cov_xdelta = np.cov(self['x'], self['delta'])
             cov_xpdelta = np.cov(self['xp'], self['delta'])
             cov_ydelta = np.cov(self['y'], self['delta'])