diff --git a/graalpython/com.oracle.graal.python.test/src/tests/test_itertools_teedataobject.py b/graalpython/com.oracle.graal.python.test/src/tests/test_itertools_teedataobject.py
new file mode 100644
index 0000000000..07846bccec
--- /dev/null
+++ b/graalpython/com.oracle.graal.python.test/src/tests/test_itertools_teedataobject.py
@@ -0,0 +1,64 @@
+# Copyright (c) 2026, Oracle and/or its affiliates. All rights reserved.
+# DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+#
+# The Universal Permissive License (UPL), Version 1.0
+#
+# Subject to the condition set forth below, permission is hereby granted to any
+# person obtaining a copy of this software, associated documentation and/or
+# data (collectively the "Software"), free of charge and under any and all
+# copyright rights in the Software, and any and all patent rights owned or
+# freely licensable by each licensor hereunder covering either (i) the
+# unmodified Software as contributed to or provided by such licensor, or (ii)
+# the Larger Works (as defined below), to deal in both
+#
+# (a) the Software, and
+#
+# (b) any piece of software and/or hardware listed in the lrgrwrks.txt file if
+# one is included with the Software each a "Larger Work" to which the Software
+# is contributed by such licensors),
+#
+# without restriction, including without limitation the rights to copy, create
+# derivative works of, display, perform, and distribute the Software and make,
+# use, sell, offer for sale, import, export, have made, and have sold the
+# Software and the Larger Work(s), and to sublicense the foregoing rights on
+# either these or other terms.
+#
+# This license is subject to the following condition:
+#
+# The above copyright notice and either this complete permission notice or at a
+# minimum a reference to the UPL must be included in all copies or substantial
+# portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+# SOFTWARE.
+import itertools
+
+
+def assert_raises(err, fn, *args, **kwargs):
+    raised = False
+    try:
+        fn(*args, **kwargs)
+    except err:
+        raised = True
+    assert raised
+
+
+def test_teedataobject_rejects_none_values():
+    assert_raises(TypeError, itertools._tee_dataobject, iter([]), None, None)
+    assert_raises(TypeError, itertools._tee_dataobject, iter([]), None, 5)
+
+
+def test_teedataobject_requires_three_arguments():
+    assert_raises(TypeError, itertools._tee_dataobject)
+    assert_raises(TypeError, itertools._tee_dataobject, 1)
+    assert_raises(TypeError, itertools._tee_dataobject, iter([]), [])
+
+
+def test_teedataobject_list_values():
+    t = itertools._tee_dataobject(iter([]), [1, 2], None)
+    assert type(t) is itertools._tee_dataobject
diff --git a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/itertools/TeeDataObjectBuiltins.java b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/itertools/TeeDataObjectBuiltins.java
index 6c4e578458..0cd35b10d5 100644
--- a/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/itertools/TeeDataObjectBuiltins.java
+++ b/graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/itertools/TeeDataObjectBuiltins.java
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2021, 2025, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2021, 2026, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * The Universal Permissive License (UPL), Version 1.0
@@ -119,7 +119,7 @@ PTeeDataObject construct(Object cls, Object[] arguments, PKeyword[] keywords,
     }
 
     @Slot(value = SlotKind.tp_init, isComplex = true)
-    @SlotSignature(name = "TeeDataObject", minNumOfPositionalArgs = 1, parameterNames = {"$self", "it", "values", "nxt"})
+    @SlotSignature(name = "TeeDataObject", minNumOfPositionalArgs = 4, parameterNames = {"$self", "it", "values", "nxt"})
     @ArgumentClinic(name = "values", defaultValue = "PNone.NONE", useDefaultForNone = true)
     @ArgumentClinic(name = "nxt", defaultValue = "PNone.NONE", useDefaultForNone = true)
     @GenerateNodeFactory
@@ -132,26 +132,6 @@ protected ArgumentClinicProvider getArgumentClinic() {
 
         abstract Object execute(VirtualFrame frame, PTeeDataObject self, Object it, Object values, Object nxt);
 
-        @Specialization(guards = "isNone(values)")
-        static Object init(PTeeDataObject self, Object it, @SuppressWarnings("unused") Object values, @SuppressWarnings("unused") PNone nxt) {
-            init(self, it, null);
-            return PNone.NONE;
-        }
-
-        @Specialization(guards = "isNone(values)")
-        static Object init(PTeeDataObject self, Object it, @SuppressWarnings("unused") Object values, PTeeDataObject nxt) {
-            init(self, it, nxt);
-            return PNone.NONE;
-        }
-
-        private static void init(PTeeDataObject self, Object it, PTeeDataObject nxt) {
-            self.setIt(it);
-            self.setValues(new Object[LINKCELLS]);
-            self.setNumread(0);
-            self.setRunning(false);
-            self.setNextlink(nxt);
-        }
-
         @Specialization
         static Object init(VirtualFrame frame, PTeeDataObject self, Object it, PList values, Object nxt,
                         @Bind Node inliningTarget,
@@ -182,7 +162,7 @@ static Object init(VirtualFrame frame, PTeeDataObject self, Object it, PList val
         }
 
         @SuppressWarnings("unused")
-        @Specialization(guards = {"!isList(values)", "!isNone(values)"})
+        @Specialization(guards = "!isList(values)")
         static Object init(VirtualFrame frame, PTeeDataObject self, Object it, Object values, Object nxt,
                         @Bind Node inliningTarget) {
             throw PRaiseNode.raiseStatic(inliningTarget, TypeError, ARG_D_MUST_BE_S_NOT_P, "teedataobject()", 2, "list", values);