diff --git a/emle/models/_emle.py b/emle/models/_emle.py
index c2db9fc..5dc8a37 100644
--- a/emle/models/_emle.py
+++ b/emle/models/_emle.py
@@ -241,6 +241,8 @@ def __init__(
                     raise ValueError(
                         "All elements of 'species' must be greater than zero"
                     )
+                # Use the custom species.
+                self._species = species
             else:
                 # Use the default species.
                 species = self._species