diff --git a/ms2rescore/retention_time.py b/ms2rescore/retention_time.py
index c58914a2..d4ed6684 100644
--- a/ms2rescore/retention_time.py
+++ b/ms2rescore/retention_time.py
@@ -63,6 +63,10 @@ def __init__(
         self.calibration_set_size = calibration_set_size
         self.num_cpu = num_cpu
 
+        # Until fixed upstream: https://github.com/compomics/DeepLC/issues/19
+        if "NUMEXPR_MAX_THREADS" not in os.environ:
+            os.environ['NUMEXPR_MAX_THREADS'] = str(self.num_cpu)
+
         from deeplc import DeepLC
 
         self.deeplc_predictor = DeepLC(