diff --git a/pyfstat.py b/pyfstat.py
index 111f160f48e5fae1d81cfe69291444b8d336af8c..391f49cd2c8303f408e88d8a413ab48ecb8b8c07 100755
--- a/pyfstat.py
+++ b/pyfstat.py
@@ -2173,7 +2173,7 @@ class MCMCFollowUpSearch(MCMCSemiCoherentSearch):
             DeltaAlpha = self.get_width_from_prior(self.theta_prior, 'Alpha')
             DeltaDelta = self.get_width_from_prior(self.theta_prior, 'Delta')
             DeltaMid = self.get_mid_from_prior(self.theta_prior, 'Delta')
-            DeltaOmega = np.sin(DeltaMid) * DeltaDelta * DeltaAlpha
+            DeltaOmega = np.sin(np.pi/2 - DeltaMid) * DeltaDelta * DeltaAlpha
             logging.info('Search over Alpha and Delta')
         else:
             logging.info('No sky search requested')