How to preform 1NN with single centroid per class in SAS?

Question

I've computer a single centroid per class using PROC fastclus in SAS,

proc fastclus data=sample.samples_train mean=knn.clusters
maxc=1 *number of clusters*
maxiter=100;
var &predictors; 
by class;
run;

I'm trying to classify a test set based on the closest one of these centroids created. This i'm doing using PROC discrim in also in SAS.

proc discrim data=knn.clusters   
             test=sample.samples_test
             method=NPAR k=1 metric=identity noclassify;
      class class; 
      var &predictors; 
      ods output ErrorTestClass=knn.error;
run; 

I'm using the euclidean distance measure with the option metric=identity.

The following error is returned.

ERROR: There are not enough observations to evaluate the pooled covariance matrix in DATA= data set or BY group.

This works if I set the number of cluster in fastproc equal to 2.

How do I however preform a 1NN with single centroid per class in SAS?