diff --git a/CHANGELOG b/CHANGELOG
index 63076fab..bd4d09b3 100644
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -15,6 +15,11 @@ Bug Fixes
 
 * Fix statement splitting (issue845).
 * Fix a late-binding closure bug in `TokenList.token_not_matching`.
+* Fix non-idempotent reindent output when a comma in an identifier list is
+  preceded by more than one whitespace token (e.g. ``a  ,  b``). Previously
+  only a single whitespace token before a comma was stripped, leaving a stray
+  space that was removed on a subsequent format pass. All whitespace before a
+  comma is now removed.
 
 
 Release 0.5.5 (Dec 19, 2025)
diff --git a/sqlparse/filters/others.py b/sqlparse/filters/others.py
index 95bc436c..fb3d2ba9 100644
--- a/sqlparse/filters/others.py
+++ b/sqlparse/filters/others.py
@@ -98,12 +98,18 @@ def _stripws_default(tlist):
             is_first_char = False
 
     def _stripws_identifierlist(self, tlist):
-        # Removes newlines before commas, see issue140
-        last_nl = None
+        # Removes whitespace before commas, see issue140. All consecutive
+        # whitespace tokens before a comma are removed so that the result is
+        # stable when the formatter is applied to its own output (issue140
+        # only handled a single preceding whitespace token, which left a
+        # stray space when the comma was preceded by multiple whitespace
+        # tokens, e.g. ``a  ,  b``).
+        last_ws = []
         for token in list(tlist.tokens):
-            if last_nl and token.ttype is T.Punctuation and token.value == ',':
-                tlist.tokens.remove(last_nl)
-            last_nl = token if token.is_whitespace else None
+            if last_ws and token.ttype is T.Punctuation and token.value == ',':
+                for ws in last_ws:
+                    tlist.tokens.remove(ws)
+            last_ws = last_ws + [token] if token.is_whitespace else []
 
             # next_ = tlist.token_next(token, skip_ws=False)
             # if (next_ and not next_.is_whitespace and
diff --git a/tests/test_format.py b/tests/test_format.py
index 0cdbcf88..168361b3 100644
--- a/tests/test_format.py
+++ b/tests/test_format.py
@@ -491,6 +491,27 @@ def test_identifier_list(self):
             'from a,',
             '     b'])
 
+    def test_identifier_list_whitespace_before_comma(self):
+        # issue140 only removed a single whitespace token before a comma, so
+        # input with multiple whitespace tokens before a comma left a stray
+        # space (``a ,``) which made formatting non-idempotent. All whitespace
+        # before a comma must be removed.
+        f = lambda sql: sqlparse.format(sql, reindent=True)
+        expected = '\n'.join([
+            'select a,',
+            '       b',
+            'from t'])
+        for s in (
+            'select a  ,  b from t',   # multiple spaces before comma
+            'select a   , b from t',   # several spaces before comma
+            'select a\t\t, b from t',  # tabs before comma
+            'select a \n , b from t',  # newline + space before comma
+        ):
+            formatted = f(s)
+            assert formatted == expected
+            # formatting must be idempotent
+            assert f(formatted) == formatted
+
     def test_identifier_list_with_wrap_after(self):
         f = lambda sql: sqlparse.format(sql, reindent=True, wrap_after=14)
         s = 'select foo, bar, baz from table1, table2 where 1 = 2'