diff --git a/Utilities/Generic/MATLAB/Functions/diagMetric.m b/Utilities/Generic/MATLAB/Functions/diagMetric.m
index 890d3f9980952ba06fbed7f430650681beb468e2..7bbc49724b5f993df38edf46beb79baaab9575d6 100644
--- a/Utilities/Generic/MATLAB/Functions/diagMetric.m
+++ b/Utilities/Generic/MATLAB/Functions/diagMetric.m
@@ -69,7 +69,7 @@ function diagonality = diagMetric(mat, matNorm, normalise)
     % Validate input arguments
     % ====================================================
     % Validate mandatory arguments
-    validateattributes(mat, "numeric", {'3d', 'square', 'nonempty'}, mfilename, "Matrices to be checked for diagonality", 1);
+    validateattributes(mat, "numeric", {'3d', 'nonempty', 'size', [NaN, size(mat, 1), NaN]}, mfilename, "Matrices to be checked for diagonality", 1);
 
     % Validate optional arguments
     if nargin > 1 && ~isempty(matNorm)