diff --git a/CHANGELOG.md b/CHANGELOG.md
index b0b7dd0..28c8041 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -18,6 +18,7 @@ Activate / deactivate all masks using MA layers
 
 - added: scene resolution in json crop pixels information, per objects
 - changed: fixed name `crop_infos.json` for exported crop pixels information
+- changed: auto-crop ignore `MA_` prefixed layers
 
 1.3.5
 
diff --git a/fn.py b/fn.py
index 544904e..0f95799 100644
--- a/fn.py
+++ b/fn.py
@@ -1341,7 +1341,7 @@ def get_gp_box_all_frame_selection(oblist=None, scn=None, cam=None, timeout=40):
             scn.frame_set(num)
             for ob in oblist:
                 for l in ob.data.layers:
-                    if l.hide or l.opacity == 0.0:
+                    if l.hide or l.opacity == 0.0 or l.info.startswith('MA_'): # hardcoded Mask exclusion !
                         continue
                     if not l.active_frame:
                         continue
@@ -1358,7 +1358,7 @@ def get_gp_box_all_frame_selection(oblist=None, scn=None, cam=None, timeout=40):
         for ob in oblist:
             # if object is not animated no need to frame_set to update object position
             for l in ob.data.layers:
-                if l.hide or l.opacity == 0.0:
+                if l.hide or l.opacity == 0.0 or l.info.startswith('MA_'): # hardcoded Mask exclusion !
                     continue
                 for f in l.frames:
                     if time() - t0 > timeout: