diff --git a/slothy/helper.py b/slothy/helper.py
index 41ca1be9..5521d1d9 100644
--- a/slothy/helper.py
+++ b/slothy/helper.py
@@ -503,6 +503,9 @@ def change_funcname(line):
             s = re.sub( f"{old_funcname}:", f"{new_funcname}:", s)
             s = re.sub( f"\\.global(\\s+){old_funcname}", f".global\\1{new_funcname}", s)
             s = re.sub( f"\\.type(\\s+){old_funcname}", f".type\\1{new_funcname}", s)
+            # On Mac, function names often start with an underscore
+            s = re.sub( f"\\.global(\\s+)_{old_funcname}", f".global\\1_{new_funcname}", s)
+            s = re.sub( f"\\.type(\\s+)_{old_funcname}", f".type\\1_{new_funcname}", s)
             return line.copy().set_text(s)
         return [ change_funcname(s) for s in source ]