diff --git a/circ_vmpdf.m b/circ_vmpdf.m
index 7d158c3..11cc2ff 100644
--- a/circ_vmpdf.m
+++ b/circ_vmpdf.m
@@ -42,6 +42,5 @@
 alpha = alpha(:);
 
 % evaluate pdf
-C = 1/(2*pi*besseli(0,kappa));
-p = C * exp(kappa*cos(alpha-thetahat));
+p = exp( kappa*(cos(alpha-thetahat)-1) ) / (2*pi*besseli(0,kappa,1));
 end