diff --git a/tools/aapt2/java/ClassDefinition.cpp b/tools/aapt2/java/ClassDefinition.cpp
index 45130a4d76812..6ad0dd68cb6ae 100644
--- a/tools/aapt2/java/ClassDefinition.cpp
+++ b/tools/aapt2/java/ClassDefinition.cpp
@@ -39,6 +39,17 @@ void MethodDefinition::WriteToStream(const StringPiece& prefix, bool final,
   *out << prefix << "}";
 }
 
+ClassDefinition::Result ClassDefinition::AddMember(std::unique_ptr<ClassMember> member) {
+  Result result = Result::kAdded;
+  auto iter = members_.find(member);
+  if (iter != members_.end()) {
+    members_.erase(iter);
+    result = Result::kOverridden;
+  }
+  members_.insert(std::move(member));
+  return result;
+}
+
 bool ClassDefinition::empty() const {
   for (const std::unique_ptr<ClassMember>& member : members_) {
     if (!member->empty()) {
diff --git a/tools/aapt2/java/ClassDefinition.h b/tools/aapt2/java/ClassDefinition.h
index ca76421390d6a..6c4bcad83d2ab 100644
--- a/tools/aapt2/java/ClassDefinition.h
+++ b/tools/aapt2/java/ClassDefinition.h
@@ -18,6 +18,7 @@
 #define AAPT_JAVA_CLASSDEFINITION_H
 
 #include <ostream>
+#include <set>
 #include <string>
 
 #include "android-base/macros.h"
@@ -37,10 +38,14 @@ class ClassMember {
  public:
   virtual ~ClassMember() = default;
 
-  AnnotationProcessor* GetCommentBuilder() { return &processor_; }
+  AnnotationProcessor* GetCommentBuilder() {
+    return &processor_;
+  }
 
   virtual bool empty() const = 0;
 
+  virtual const std::string& GetName() const = 0;
+
   // Writes the class member to the out stream. Subclasses should derive this method
   // to write their own data. Call this base method from the subclass to write out
   // this member's comments/annotations.
@@ -57,7 +62,13 @@ class PrimitiveMember : public ClassMember {
   PrimitiveMember(const android::StringPiece& name, const T& val)
       : name_(name.to_string()), val_(val) {}
 
-  bool empty() const override { return false; }
+  bool empty() const override {
+    return false;
+  }
+
+  const std::string& GetName() const override {
+    return name_;
+  }
 
   void WriteToStream(const android::StringPiece& prefix, bool final,
                      std::ostream* out) const override {
@@ -83,7 +94,13 @@ class PrimitiveMember<std::string> : public ClassMember {
   PrimitiveMember(const android::StringPiece& name, const std::string& val)
       : name_(name.to_string()), val_(val) {}
 
-  bool empty() const override { return false; }
+  bool empty() const override {
+    return false;
+  }
+
+  const std::string& GetName() const override {
+    return name_;
+  }
 
   void WriteToStream(const android::StringPiece& prefix, bool final,
                      std::ostream* out) const override {
@@ -109,9 +126,17 @@ class PrimitiveArrayMember : public ClassMember {
  public:
   explicit PrimitiveArrayMember(const android::StringPiece& name) : name_(name.to_string()) {}
 
-  void AddElement(const T& val) { elements_.push_back(val); }
+  void AddElement(const T& val) {
+    elements_.push_back(val);
+  }
 
-  bool empty() const override { return false; }
+  bool empty() const override {
+    return false;
+  }
+
+  const std::string& GetName() const override {
+    return name_;
+  }
 
   void WriteToStream(const android::StringPiece& prefix, bool final,
                      std::ostream* out) const override {
@@ -154,6 +179,11 @@ class MethodDefinition : public ClassMember {
   // formatting may be broken.
   void AppendStatement(const android::StringPiece& statement);
 
+  // Not quite the same as a name, but good enough.
+  const std::string& GetName() const override {
+    return signature_;
+  }
+
   // Even if the method is empty, we always want to write the method signature.
   bool empty() const override { return false; }
 
@@ -175,19 +205,34 @@ class ClassDefinition : public ClassMember {
   ClassDefinition(const android::StringPiece& name, ClassQualifier qualifier, bool createIfEmpty)
       : name_(name.to_string()), qualifier_(qualifier), create_if_empty_(createIfEmpty) {}
 
-  void AddMember(std::unique_ptr<ClassMember> member) {
-    members_.push_back(std::move(member));
-  }
+  enum class Result {
+    kAdded,
+    kOverridden,
+  };
+
+  Result AddMember(std::unique_ptr<ClassMember> member);
 
   bool empty() const override;
+
+  const std::string& GetName() const override {
+    return name_;
+  }
+
   void WriteToStream(const android::StringPiece& prefix, bool final,
                      std::ostream* out) const override;
 
  private:
+  struct ClassMemberCompare {
+    using T = std::unique_ptr<ClassMember>;
+    bool operator()(const T& a, const T& b) const {
+      return a->GetName() < b->GetName();
+    }
+  };
+
   std::string name_;
   ClassQualifier qualifier_;
   bool create_if_empty_;
-  std::vector<std::unique_ptr<ClassMember>> members_;
+  std::set<std::unique_ptr<ClassMember>, ClassMemberCompare> members_;
 
   DISALLOW_COPY_AND_ASSIGN(ClassDefinition);
 };
diff --git a/tools/aapt2/java/ManifestClassGenerator.cpp b/tools/aapt2/java/ManifestClassGenerator.cpp
index 4ef32c92dd848..c4b36176aa71a 100644
--- a/tools/aapt2/java/ManifestClassGenerator.cpp
+++ b/tools/aapt2/java/ManifestClassGenerator.cpp
@@ -68,7 +68,10 @@ static bool WriteSymbol(const Source& source, IDiagnostics* diag, xml::Element*
       util::make_unique<StringMember>(result.value(), attr->value);
   string_member->GetCommentBuilder()->AppendComment(el->comment);
 
-  class_def->AddMember(std::move(string_member));
+  if (class_def->AddMember(std::move(string_member)) == ClassDefinition::Result::kOverridden) {
+    diag->Warn(DiagMessage(source.WithLine(el->line_number))
+               << "duplicate definitions of '" << result.value() << "', overriding previous");
+  }
   return true;
 }
 
diff --git a/tools/aapt2/java/ManifestClassGenerator_test.cpp b/tools/aapt2/java/ManifestClassGenerator_test.cpp
index c744e9bd4fc9b..ada563409d19b 100644
--- a/tools/aapt2/java/ManifestClassGenerator_test.cpp
+++ b/tools/aapt2/java/ManifestClassGenerator_test.cpp
@@ -121,6 +121,21 @@ TEST(ManifestClassGeneratorTest, CommentsAndAnnotationsArePresent) {
   EXPECT_THAT(actual, HasSubstr(expected_test));
 }
 
+// This is bad but part of public API behaviour so we need to preserve it.
+TEST(ManifestClassGeneratorTest, LastSeenPermissionWithSameLeafNameTakesPrecedence) {
+  std::unique_ptr<IAaptContext> context = test::ContextBuilder().Build();
+  std::unique_ptr<xml::XmlResource> manifest = test::BuildXmlDom(R"(
+      <manifest xmlns:android="http://schemas.android.com/apk/res/android">
+        <permission android:name="android.permission.ACCESS_INTERNET" />
+        <permission android:name="com.android.aapt.test.ACCESS_INTERNET" />
+      </manifest>)");
+
+  std::string actual;
+  ASSERT_TRUE(GetManifestClassText(context.get(), manifest.get(), &actual));
+  EXPECT_THAT(actual, HasSubstr("ACCESS_INTERNET=\"com.android.aapt.test.ACCESS_INTERNET\";"));
+  EXPECT_THAT(actual, Not(HasSubstr("ACCESS_INTERNET=\"android.permission.ACCESS_INTERNET\";")));
+}
+
 static ::testing::AssertionResult GetManifestClassText(IAaptContext* context, xml::XmlResource* res,
                                                        std::string* out_str) {
   std::unique_ptr<ClassDefinition> manifest_class =