diff --git a/pkg/analyzer/lib/src/dart/sdk/patch.dart b/pkg/analyzer/lib/src/dart/sdk/patch.dart
index 02b497cf392..44d48cb1cdf 100644
--- a/pkg/analyzer/lib/src/dart/sdk/patch.dart
+++ b/pkg/analyzer/lib/src/dart/sdk/patch.dart
@@ -100,9 +100,26 @@ class SdkPatcher {
 
   void _patchClassMembers(
       ClassDeclaration baseClass, ClassDeclaration patchClass) {
+    String className = baseClass.name.name;
     List<ClassMember> membersToAppend = [];
     for (ClassMember patchMember in patchClass.members) {
-      if (patchMember is MethodDeclaration) {
+      if (patchMember is FieldDeclaration) {
+        if (_hasPatchAnnotation(patchMember.metadata)) {
+          _failInPatch('attempts to patch a field', patchMember.offset);
+        }
+        List<VariableDeclaration> fields = patchMember.fields.variables;
+        if (fields.length != 1) {
+          _failInPatch('contains a field declaration with more than one field',
+              patchMember.offset);
+        }
+        String name = fields[0].name.name;
+        if (!Identifier.isPrivateName(className) &&
+            !Identifier.isPrivateName(name)) {
+          // TODO(scheglov) allow adding public fields into dart:_internal
+          _failInPatch('contains a public field', patchMember.offset);
+        }
+        membersToAppend.add(patchMember);
+      } else if (patchMember is MethodDeclaration) {
         String name = patchMember.name.name;
         if (_hasPatchAnnotation(patchMember.metadata)) {
           for (ClassMember baseMember in baseClass.members) {
@@ -181,7 +198,7 @@ class SdkPatcher {
           }
         } else {
           if (name == null) {
-            if (!Identifier.isPrivateName(baseClass.name.name)) {
+            if (!Identifier.isPrivateName(className)) {
               _failInPatch(
                   'contains an unnamed public constructor', patchMember.offset);
             }
@@ -191,7 +208,6 @@ class SdkPatcher {
           membersToAppend.add(patchMember);
         }
       } else {
-        // TODO(scheglov) support field
         String className = patchClass.name.name;
         _failInPatch('contains an unsupported class member in $className',
             patchMember.offset);
diff --git a/pkg/analyzer/test/src/dart/sdk/patch_test.dart b/pkg/analyzer/test/src/dart/sdk/patch_test.dart
index 840d4c5280c..5b4422b52e6 100644
--- a/pkg/analyzer/test/src/dart/sdk/patch_test.dart
+++ b/pkg/analyzer/test/src/dart/sdk/patch_test.dart
@@ -226,6 +226,96 @@ class C {
     _assertPrevNextToken(constructor.endToken, clazz.rightBracket);
   }
 
+  test_class_field_append() {
+    CompilationUnit unit = _doTopLevelPatching(
+        r'''
+class C {
+  void a() {}
+}
+''',
+        r'''
+@patch
+class C {
+  int _b = 42;
+}
+''');
+    _assertUnitCode(unit, 'class C {void a() {} int _b = 42;}');
+    ClassDeclaration clazz = unit.declarations[0];
+    MethodDeclaration a = clazz.members[0];
+    FieldDeclaration b = clazz.members[1];
+    _assertPrevNextToken(a.endToken, b.beginToken);
+    _assertPrevNextToken(b.endToken, clazz.rightBracket);
+  }
+
+  test_class_field_append_fail_moreThanOne() {
+    expect(() {
+      _doTopLevelPatching(
+          r'''
+class A {}
+''',
+          r'''
+@patch
+class A {
+  @patch
+  int _f1, _f2;
+}
+''');
+    }, throwsArgumentError);
+  }
+
+  test_class_field_append_fail_notPrivate() {
+    expect(() {
+      _doTopLevelPatching(
+          r'''
+class A {}
+''',
+          r'''
+@patch
+class A {
+  @patch
+  int b;
+}
+''');
+    }, throwsArgumentError);
+  }
+
+  test_class_field_append_publiInPrivateClass() {
+    CompilationUnit unit = _doTopLevelPatching(
+        r'''
+class _C {
+  void a() {}
+}
+''',
+        r'''
+@patch
+class _C {
+  int b = 42;
+}
+''');
+    _assertUnitCode(unit, 'class _C {void a() {} int b = 42;}');
+    ClassDeclaration clazz = unit.declarations[0];
+    MethodDeclaration a = clazz.members[0];
+    FieldDeclaration b = clazz.members[1];
+    _assertPrevNextToken(a.endToken, b.beginToken);
+    _assertPrevNextToken(b.endToken, clazz.rightBracket);
+  }
+
+  test_class_field_patch_fail() {
+    expect(() {
+      _doTopLevelPatching(
+          r'''
+class A {}
+''',
+          r'''
+@patch
+class A {
+  @patch
+  int _f;
+}
+''');
+    }, throwsArgumentError);
+  }
+
   test_class_getter_append() {
     CompilationUnit unit = _doTopLevelPatching(
         r'''