diff --git a/clang/lib/Format/NamespaceEndCommentsFixer.cpp b/clang/lib/Format/NamespaceEndCommentsFixer.cpp
--- a/clang/lib/Format/NamespaceEndCommentsFixer.cpp
+++ b/clang/lib/Format/NamespaceEndCommentsFixer.cpp
@@ -180,9 +180,13 @@
   if (NamespaceTok->is(tok::l_brace)) {
     // "namespace" keyword can be on the line preceding '{', e.g. in styles
     // where BraceWrapping.AfterNamespace is true.
-    if (StartLineIndex > 0)
+    if (StartLineIndex > 0) {
       NamespaceTok = AnnotatedLines[StartLineIndex - 1]->First;
+      if (AnnotatedLines[StartLineIndex - 1]->endsWith(tok::semi))
+        return nullptr;
+    }
   }
+
   return NamespaceTok->getNamespaceToken();
 }
 
diff --git a/clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp b/clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp
--- a/clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp
+++ b/clang/unittests/Format/NamespaceEndCommentsFixerTest.cpp
@@ -1185,6 +1185,82 @@
                                     "}\n",
                                     Style));
 }
+
+TEST_F(ShortNamespaceLinesTest, NamespaceAlias) {
+  auto Style = getLLVMStyle();
+
+  EXPECT_EQ("namespace n = nn;\n"
+            "{\n"
+            "  int i;\n"
+            "  int j;\n"
+            "}\n",
+            fixNamespaceEndComments("namespace n = nn;\n"
+                                    "{\n"
+                                    "  int i;\n"
+                                    "  int j;\n"
+                                    "}\n",
+                                    Style));
+
+  EXPECT_EQ("namespace n = nn; // comment\n"
+            "{\n"
+            "  int i;\n"
+            "  int j;\n"
+            "}\n",
+            fixNamespaceEndComments("namespace n = nn; // comment\n"
+                                    "{\n"
+                                    "  int i;\n"
+                                    "  int j;\n"
+                                    "}\n",
+                                    Style));
+
+  EXPECT_EQ("namespace n = nn; /* comment */\n"
+            "{\n"
+            "  int i;\n"
+            "  int j;\n"
+            "}\n",
+            fixNamespaceEndComments("namespace n = nn; /* comment */\n"
+                                    "{\n"
+                                    "  int i;\n"
+                                    "  int j;\n"
+                                    "}\n",
+                                    Style));
+
+  EXPECT_EQ(
+      "namespace n = nn; /* comment */ /* comment2 */\n"
+      "{\n"
+      "  int i;\n"
+      "  int j;\n"
+      "}\n",
+      fixNamespaceEndComments("namespace n = nn; /* comment */ /* comment2 */\n"
+                              "{\n"
+                              "  int i;\n"
+                              "  int j;\n"
+                              "}\n",
+                              Style));
+
+  EXPECT_EQ("namespace n = nn; {\n"
+            "  int i;\n"
+            "  int j;\n"
+            "}\n",
+            fixNamespaceEndComments("namespace n = nn; {\n"
+                                    "  int i;\n"
+                                    "  int j;\n"
+                                    "}\n",
+                                    Style));
+  EXPECT_EQ("int foo;\n"
+            "namespace n\n"
+            "{\n"
+            "  int i;\n"
+            "  int j;\n"
+            "}// namespace n\n",
+            fixNamespaceEndComments("int foo;\n"
+                                    "namespace n\n"
+                                    "{\n"
+                                    "  int i;\n"
+                                    "  int j;\n"
+                                    "}\n",
+                                    Style));
+}
 } // end namespace
 } // end namespace format
 } // end namespace clang