Index: clang/lib/Format/FormatToken.h
===================================================================
--- clang/lib/Format/FormatToken.h
+++ clang/lib/Format/FormatToken.h
@@ -98,7 +98,9 @@
   TYPE(MacroBlockBegin)                                                        \
   TYPE(MacroBlockEnd)                                                          \
   TYPE(ModulePartitionColon)                                                   \
+  TYPE(NamespaceLBrace)                                                        \
   TYPE(NamespaceMacro)                                                         \
+  TYPE(NamespaceRBrace)                                                        \
   TYPE(NonNullAssertion)                                                       \
   TYPE(NullCoalescingEqual)                                                    \
   TYPE(NullCoalescingOperator)                                                 \
Index: clang/lib/Format/UnwrappedLineParser.cpp
===================================================================
--- clang/lib/Format/UnwrappedLineParser.cpp
+++ clang/lib/Format/UnwrappedLineParser.cpp
@@ -2986,10 +2986,16 @@
     if (ManageWhitesmithsBraces)
       ++Line->Level;
 
+    FormatToken *LBrace = FormatTok;
+    LBrace->setFinalizedType(TT_NamespaceLBrace);
+
     parseBlock(/*MustBeDeclaration=*/true, AddLevels, /*MunchSemi=*/true,
                /*KeepBraces=*/nullptr, /*IfKind=*/nullptr,
                ManageWhitesmithsBraces);
 
+    if (LBrace->MatchingParen)
+      LBrace->MatchingParen->setFinalizedType(TT_NamespaceRBrace);
+
     // Munch the semicolon after a namespace. This is more common than one would
     // think. Putting the semicolon into its own line is very ugly.
     if (FormatTok->is(tok::semi))
Index: clang/lib/Format/WhitespaceManager.cpp
===================================================================
--- clang/lib/Format/WhitespaceManager.cpp
+++ clang/lib/Format/WhitespaceManager.cpp
@@ -985,11 +985,10 @@
 
     if (i + 1 != e && Changes[i + 1].ContinuesPPDirective)
       ChangeMaxColumn -= 2;
-    // If this comment follows an } in column 0, it probably documents the
-    // closing of a namespace and we don't want to align it.
-    bool FollowsRBraceInColumn0 = i > 0 && Changes[i].NewlinesBefore == 0 &&
-                                  Changes[i - 1].Tok->is(tok::r_brace) &&
-                                  Changes[i - 1].StartOfTokenColumn == 0;
+
+    // We don't want to align namespace end comments.
+    bool DontAlignThisComment =
+        i > 0 && Changes[i - 1].Tok->is(TT_NamespaceRBrace);
     bool WasAlignedWithStartOfNextLine = false;
     if (Changes[i].NewlinesBefore >= 1) { // A comment on its own line.
       unsigned CommentColumn = SourceMgr.getSpellingColumnNumber(
@@ -1009,7 +1008,7 @@
       }
     }
     if (Style.AlignTrailingComments.Kind == FormatStyle::TCAS_Never ||
-        FollowsRBraceInColumn0) {
+        DontAlignThisComment) {
       alignTrailingComments(StartOfSequence, i, MinColumn);
       MinColumn = ChangeMinColumn;
       MaxColumn = ChangeMinColumn;
Index: clang/unittests/Format/FormatTest.cpp
===================================================================
--- clang/unittests/Format/FormatTest.cpp
+++ clang/unittests/Format/FormatTest.cpp
@@ -19221,7 +19221,7 @@
                "      int x;\n"
                "      };\n"
                "    } // namespace b\n"
-               "  }   // namespace a",
+               "  } // namespace a",
                WhitesmithsBraceStyle);
 
   verifyFormat("void f()\n"
Index: clang/unittests/Format/FormatTestComments.cpp
===================================================================
--- clang/unittests/Format/FormatTestComments.cpp
+++ clang/unittests/Format/FormatTestComments.cpp
@@ -68,6 +68,20 @@
     EXPECT_EQ(Code.str(), format(test::messUp(Code), Style));
   }
 
+  void verifyFormat(llvm::StringRef Expected, llvm::StringRef Code,
+                    const FormatStyle &Style = getLLVMStyle()) {
+    EXPECT_EQ(Expected.str(), format(Expected, Style))
+        << "Expected code is not stable";
+    EXPECT_EQ(Expected.str(), format(test::messUp(Code), Style));
+  }
+
+  void verifyFormatWithoutMessUp(llvm::StringRef Expected, llvm::StringRef Code,
+                                 const FormatStyle &Style = getLLVMStyle()) {
+    EXPECT_EQ(Expected.str(), format(Expected, Style))
+        << "Expected code is not stable";
+    EXPECT_EQ(Expected.str(), format(Code, Style));
+  }
+
   void verifyGoogleFormat(llvm::StringRef Code) {
     verifyFormat(Code, getGoogleStyle());
   }
@@ -3076,6 +3090,55 @@
                    Style));
 }
 
+TEST_F(FormatTestComments, DontAlignNamespaceComments) {
+  FormatStyle Style = getLLVMStyle();
+  Style.NamespaceIndentation = FormatStyle::NI_All;
+  Style.NamespaceMacros.push_back("TESTSUITE");
+  Style.ShortNamespaceLines = 0;
+
+  llvm::StringRef Input = "namespace A {\n"
+                          "  TESTSUITE(B) {\n"
+                          "    namespace C {\n"
+                          "      namespace D {} // namespace D\n"
+                          "      std::string Foo = Bar; // Comment\n"
+                          "    }          // namespace C\n"
+                          "  }\n"
+                          "} // NaMeSpAcE A";
+
+  EXPECT_EQ(Style.AlignTrailingComments.Kind, FormatStyle::TCAS_Always);
+  verifyFormat("namespace A {\n"
+               "  TESTSUITE(B) {\n"
+               "    namespace C {\n"
+               "      namespace D {} // namespace D\n"
+               "      std::string Foo = Bar; // Comment\n"
+               "    } // namespace C\n"
+               "  } // TESTSUITE(B)\n"
+               "} // NaMeSpAcE A",
+               Input, Style);
+
+  Style.AlignTrailingComments.Kind = FormatStyle::TCAS_Never;
+  verifyFormat("namespace A {\n"
+               "  TESTSUITE(B) {\n"
+               "    namespace C {\n"
+               "      namespace D {} // namespace D\n"
+               "      std::string Foo = Bar; // Comment\n"
+               "    } // namespace C\n"
+               "  } // TESTSUITE(B)\n"
+               "} // NaMeSpAcE A",
+               Input, Style);
+
+  Style.AlignTrailingComments.Kind = FormatStyle::TCAS_Leave;
+  verifyFormatWithoutMessUp("namespace A {\n"
+                            "  TESTSUITE(B) {\n"
+                            "    namespace C {\n"
+                            "      namespace D {} // namespace D\n"
+                            "      std::string Foo = Bar; // Comment\n"
+                            "    }          // namespace C\n"
+                            "  }// TESTSUITE(B)\n"
+                            "} // NaMeSpAcE A",
+                            Input, Style);
+}
+
 TEST_F(FormatTestComments, AlignsBlockCommentDecorations) {
   EXPECT_EQ("/*\n"
             " */",