diff --git a/CHANGELOG.md b/CHANGELOG.md
index b1987ac..d3d9d5b 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -44,6 +44,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 ### Fixed
 - `gpseq_anim`
     + Crash when 2D mask folder is not provided.
+    + Wrong variable name in `anim.series.Series`.
 
 ### Removed
 - `gpseq_fromfish`
diff --git a/pygpseq/anim/series.py b/pygpseq/anim/series.py
index 708d650..93c3e72 100644
--- a/pygpseq/anim/series.py
+++ b/pygpseq/anim/series.py
@@ -288,10 +288,10 @@ def find_nuclei(self, **kwargs):
 
         # Save mask
         log += self.printout('Saving series object mask...', 2)
-        if 1 == np.max(imbin):
-            L = label(imbin)
+        if 1 == np.max(mask):
+            L = label(mask)
         else:
-            L = imbin
+            L = mask
 
         # Export binary mask as TIF
         if not type(None) == type(mask_tiff_dir) and not already_segmented: