diff --git a/fmriprep/cli/parser.py b/fmriprep/cli/parser.py
index 7ae36407e..77fbb63c2 100644
--- a/fmriprep/cli/parser.py
+++ b/fmriprep/cli/parser.py
@@ -71,7 +71,7 @@ def __call__(self, parser, namespace, values, option_string=None):
                     k = f'deriv-{i_kv}'
                 else:
                     k, v = kv.split('=')
-                d[k] = os.path.abspath(v)
+                d[k] = Path(v)
             setattr(namespace, self.dest, d)
 
     def _path_exists(path, parser):
@@ -236,7 +236,7 @@ def _slice_time_ref(value, parser):
         '--derivatives',
         action=ToDict,
         metavar='PACKAGE=PATH',
-        type=Path,
+        type=str,
         nargs='*',
         help=(
             'Search PATH(s) for pre-computed derivatives. '