diff --git a/quapy/model_selection.py b/quapy/model_selection.py
index 86e79f3..0cd5d4e 100644
--- a/quapy/model_selection.py
+++ b/quapy/model_selection.py
@@ -11,7 +11,7 @@ from quapy.evaluation import artificial_prevalence_prediction, natural_prevalenc
 from quapy.method.aggregative import BaseQuantifier
 import inspect
 
-from util import _check_sample_size
+from quapy.util import _check_sample_size
 
 
 class GridSearchQ(BaseQuantifier):