diff --git a/bob/bio/gmm/algorithm/GMM.py b/bob/bio/gmm/algorithm/GMM.py
index 6ea1e4617ac79394a0cd0dc61535aba46609528d..9f39171fde81725cebd02e7f0494defef2818ce2 100644
--- a/bob/bio/gmm/algorithm/GMM.py
+++ b/bob/bio/gmm/algorithm/GMM.py
@@ -284,7 +284,7 @@ class GMM(BioAlgorithm, BaseEstimator):
         if isinstance(array, da.Array):
             array = array.persist()
 
-        logger.debug("UBM with %d feature vectors", array.shape[0])
+        logger.debug("UBM with %d feature vectors", len(array))
 
         logger.debug(f"Creating UBM machine with {self.number_of_gaussians} gaussians")