diff --git a/nimare/transforms.py b/nimare/transforms.py
index 1ffe24701..40d536cdd 100644
--- a/nimare/transforms.py
+++ b/nimare/transforms.py
@@ -108,7 +108,7 @@ def transform_images(images_df, target, masker, metadata_df=None, out_dir=None,
     images_df : :class:`pandas.DataFrame`
         DataFrame with paths to new images added.
     """
-    images_df = images_df.copy()
+    new_images_df = images_df.copy()  # Work on a copy of the images_df
 
     valid_targets = {"z", "p", "beta", "varcope"}
     if target not in valid_targets:
@@ -155,10 +155,10 @@ def transform_images(images_df, target, masker, metadata_df=None, out_dir=None,
             else:
                 LGR.debug("Image already exists. Not overwriting.")
 
-            images_df.loc[images_df["id"] == id_, target] = new_file
+            new_images_df.loc[new_images_df["id"] == id_, target] = new_file
         else:
-            images_df.loc[images_df["id"] == id_, target] = None
-    return images_df
+            new_images_df.loc[new_images_df["id"] == id_, target] = None
+    return new_images_df
 
 
 def resolve_transforms(target, available_data, masker):
diff --git a/setup.cfg b/setup.cfg
index bdfd80ec5..f035e3201 100644
--- a/setup.cfg
+++ b/setup.cfg
@@ -98,6 +98,8 @@ minimum =
     scikit-learn==1.0.0
     scipy==1.6.0
 all =
+    %(gzip)s
+    %(cbmr)s
     %(doc)s
     %(tests)s