diff --git a/inverseSHT.m b/inverseSHT.m
index 4eac8f8..c705402 100644
--- a/inverseSHT.m
+++ b/inverseSHT.m
@@ -16,7 +16,7 @@
 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
 
     % vector of spherical harmonics
-    N = sqrt(length(F_N)) - 1;
+    N = sqrt(size(F_N,1)) - 1;
     Y_N = getSH(N, dirs, basisType);
     
     % perform the inverse transform up to degree N