diff --git a/pkg/front_end/lib/src/source/fragment_factory_impl.dart b/pkg/front_end/lib/src/source/fragment_factory_impl.dart
index 24cb11af35a..dbfd205c9d4 100644
--- a/pkg/front_end/lib/src/source/fragment_factory_impl.dart
+++ b/pkg/front_end/lib/src/source/fragment_factory_impl.dart
@@ -2241,7 +2241,9 @@ class FragmentFactoryImpl implements FragmentFactory {
       modifiers |= Modifiers.SuperInitializingFormal;
     }
     bool isWildcard =
-        libraryFeatures.wildcardVariables.isEnabled && name == '_';
+        kind.isPositional &&
+        libraryFeatures.wildcardVariables.isEnabled &&
+        name == '_';
     int? wildcardIndex;
     if (isWildcard) {
       wildcardIndex = wildcardVariableIndex++;
diff --git a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.expect b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.expect
index ab3d5d6e9b4..f931463083d 100644
--- a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.expect
+++ b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.expect
@@ -26,8 +26,8 @@ class C extends core::Object {
   field core::int? __extraPrivate;
   field core::int? _123;
   field core::int? _for;
-  constructor onlyUnderscore({wildcard initializing-formal core::int? _#wc0#formal = #C1}) → self::C
-    : self::C::_for = null, self::C::_123 = null, self::C::__extraPrivate = null, self::C::_ = _#wc0#formal, super core::Object::•()
+  constructor onlyUnderscore({initializing-formal core::int? _ = #C1}) → self::C
+    : self::C::_for = null, self::C::_123 = null, self::C::__extraPrivate = null, self::C::_ = _, super core::Object::•()
     ;
   constructor stillPrivate({initializing-formal core::int? __extraPrivate = #C1}) → self::C
     : self::C::_for = null, self::C::_123 = null, self::C::_ = null, self::C::__extraPrivate = __extraPrivate, super core::Object::•()
diff --git a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.modular.expect b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.modular.expect
index ab3d5d6e9b4..f931463083d 100644
--- a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.modular.expect
+++ b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.modular.expect
@@ -26,8 +26,8 @@ class C extends core::Object {
   field core::int? __extraPrivate;
   field core::int? _123;
   field core::int? _for;
-  constructor onlyUnderscore({wildcard initializing-formal core::int? _#wc0#formal = #C1}) → self::C
-    : self::C::_for = null, self::C::_123 = null, self::C::__extraPrivate = null, self::C::_ = _#wc0#formal, super core::Object::•()
+  constructor onlyUnderscore({initializing-formal core::int? _ = #C1}) → self::C
+    : self::C::_for = null, self::C::_123 = null, self::C::__extraPrivate = null, self::C::_ = _, super core::Object::•()
     ;
   constructor stillPrivate({initializing-formal core::int? __extraPrivate = #C1}) → self::C
     : self::C::_for = null, self::C::_123 = null, self::C::_ = null, self::C::__extraPrivate = __extraPrivate, super core::Object::•()
diff --git a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.outline.expect b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.outline.expect
index ec580ea4c48..20931a8c069 100644
--- a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.outline.expect
+++ b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.outline.expect
@@ -26,7 +26,7 @@ class C extends core::Object {
   field core::int? __extraPrivate;
   field core::int? _123;
   field core::int? _for;
-  constructor onlyUnderscore({wildcard initializing-formal core::int? _#wc0#formal = null}) → self::C
+  constructor onlyUnderscore({initializing-formal core::int? _ = null}) → self::C
     ;
   constructor stillPrivate({initializing-formal core::int? __extraPrivate = null}) → self::C
     ;
diff --git a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.transformed.expect b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.transformed.expect
index ab3d5d6e9b4..f931463083d 100644
--- a/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.transformed.expect
+++ b/pkg/front_end/testcases/private_named_parameters/no_corresponding_public_name.dart.strong.transformed.expect
@@ -26,8 +26,8 @@ class C extends core::Object {
   field core::int? __extraPrivate;
   field core::int? _123;
   field core::int? _for;
-  constructor onlyUnderscore({wildcard initializing-formal core::int? _#wc0#formal = #C1}) → self::C
-    : self::C::_for = null, self::C::_123 = null, self::C::__extraPrivate = null, self::C::_ = _#wc0#formal, super core::Object::•()
+  constructor onlyUnderscore({initializing-formal core::int? _ = #C1}) → self::C
+    : self::C::_for = null, self::C::_123 = null, self::C::__extraPrivate = null, self::C::_ = _, super core::Object::•()
     ;
   constructor stillPrivate({initializing-formal core::int? __extraPrivate = #C1}) → self::C
     : self::C::_for = null, self::C::_123 = null, self::C::_ = null, self::C::__extraPrivate = __extraPrivate, super core::Object::•()
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart
new file mode 100644
index 00000000000..7f6424e4853
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart
@@ -0,0 +1,17 @@
+// Copyright (c) 2026, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+void f1({int _ = 0}) {}
+void f2({int _ = 0, String _ = ''}) {}
+
+class C {
+  int _;
+  C({this._ = 0});
+}
+
+test() {
+  f1(_: 1);
+  f2(_: 2);
+  C(_: 3);
+}
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.expect b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.expect
new file mode 100644
index 00000000000..bba1340c50f
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.expect
@@ -0,0 +1,48 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:5:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f1({int _ = 0}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: Duplicated parameter name '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Context: Other parameter named '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:10:11: Error: A private named parameter must have a corresponding public name.
+//   C({this._ = 0});
+//           ^
+//
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  field core::int _;
+  constructor •({initializing-formal core::int _ = #C1}) → self::C
+    : self::C::_ = _, super core::Object::•()
+    ;
+}
+static method f1({core::int _ = #C1}) → void {}
+static method f2({core::int _ = #C1, core::String _ = #C2}) → void {}
+static method test() → dynamic {
+  self::f1(_: 1);
+  self::f2(_: 2);
+  new self::C::•(_: 3);
+}
+
+constants  {
+  #C1 = 0
+  #C2 = ""
+}
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.modular.expect b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.modular.expect
new file mode 100644
index 00000000000..bba1340c50f
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.modular.expect
@@ -0,0 +1,48 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:5:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f1({int _ = 0}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: Duplicated parameter name '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Context: Other parameter named '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:10:11: Error: A private named parameter must have a corresponding public name.
+//   C({this._ = 0});
+//           ^
+//
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  field core::int _;
+  constructor •({initializing-formal core::int _ = #C1}) → self::C
+    : self::C::_ = _, super core::Object::•()
+    ;
+}
+static method f1({core::int _ = #C1}) → void {}
+static method f2({core::int _ = #C1, core::String _ = #C2}) → void {}
+static method test() → dynamic {
+  self::f1(_: 1);
+  self::f2(_: 2);
+  new self::C::•(_: 3);
+}
+
+constants  {
+  #C1 = 0
+  #C2 = ""
+}
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.outline.expect b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.outline.expect
new file mode 100644
index 00000000000..4da11cc325e
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.outline.expect
@@ -0,0 +1,41 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:5:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f1({int _ = 0}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: Duplicated parameter name '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Context: Other parameter named '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:10:11: Error: A private named parameter must have a corresponding public name.
+//   C({this._ = 0});
+//           ^
+//
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  field core::int _;
+  constructor •({initializing-formal core::int _ = 0}) → self::C
+    ;
+}
+static method f1({has-declared-initializer core::int _}) → void
+  ;
+static method f2({has-declared-initializer core::int _, has-declared-initializer core::String _}) → void
+  ;
+static method test() → dynamic
+  ;
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.transformed.expect b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.transformed.expect
new file mode 100644
index 00000000000..bba1340c50f
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.strong.transformed.expect
@@ -0,0 +1,48 @@
+library;
+//
+// Problems in library:
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:5:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f1({int _ = 0}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: A named parameter that doesn't refer to an instance variable can't start with an underscore ('_').
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:28: Error: Duplicated parameter name '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//                            ^
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:6:14: Context: Other parameter named '_'.
+// void f2({int _ = 0, String _ = ''}) {}
+//              ^
+//
+// pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart:10:11: Error: A private named parameter must have a corresponding public name.
+//   C({this._ = 0});
+//           ^
+//
+import self as self;
+import "dart:core" as core;
+
+class C extends core::Object {
+  field core::int _;
+  constructor •({initializing-formal core::int _ = #C1}) → self::C
+    : self::C::_ = _, super core::Object::•()
+    ;
+}
+static method f1({core::int _ = #C1}) → void {}
+static method f2({core::int _ = #C1, core::String _ = #C2}) → void {}
+static method test() → dynamic {
+  self::f1(_: 1);
+  self::f2(_: 2);
+  new self::C::•(_: 3);
+}
+
+constants  {
+  #C1 = 0
+  #C2 = ""
+}
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.textual_outline.expect b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.textual_outline.expect
new file mode 100644
index 00000000000..15b8dd0109d
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.textual_outline.expect
@@ -0,0 +1,10 @@
+void f1({int _ = 0}) {}
+
+void f2({int _ = 0, String _ = ''}) {}
+
+class C {
+  int _;
+  C({this._ = 0});
+}
+
+test() {}
diff --git a/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.textual_outline_modelled.expect b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.textual_outline_modelled.expect
new file mode 100644
index 00000000000..65ec4727541
--- /dev/null
+++ b/pkg/front_end/testcases/private_named_parameters/wildcard_named_parameters.dart.textual_outline_modelled.expect
@@ -0,0 +1,10 @@
+class C {
+  C({this._ = 0});
+  int _;
+}
+
+test() {}
+
+void f1({int _ = 0}) {}
+
+void f2({int _ = 0, String _ = ''}) {}