Index: cfe/trunk/lib/Format/WhitespaceManager.cpp
===================================================================
--- cfe/trunk/lib/Format/WhitespaceManager.cpp
+++ cfe/trunk/lib/Format/WhitespaceManager.cpp
@@ -164,8 +164,9 @@
   const WhitespaceManager::Change *LastBlockComment = nullptr;
   for (auto &Change : Changes) {
     // Reset the IsTrailingComment flag for changes inside of trailing comments
-    // so they don't get realigned later.
-    if (Change.IsInsideToken)
+    // so they don't get realigned later. Comment line breaks however still need
+    // to be aligned.
+    if (Change.IsInsideToken && Change.NewlinesBefore == 0)
       Change.IsTrailingComment = false;
     Change.StartOfBlockComment = nullptr;
     Change.IndentationOffset = 0;
Index: cfe/trunk/unittests/Format/FormatTest.cpp
===================================================================
--- cfe/trunk/unittests/Format/FormatTest.cpp
+++ cfe/trunk/unittests/Format/FormatTest.cpp
@@ -11852,6 +11852,40 @@
                    "             // line 3\n"
                    "          b);",
                    getLLVMStyleWithColumns(40)));
+
+  // Align newly broken trailing comments.
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n",
+            format("int ab; // line\n"
+                   "int a; // long long\n",
+                   getLLVMStyleWithColumns(15)));
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n"
+            "        // long",
+            format("int ab; // line\n"
+                   "int a; // long long\n"
+                   "       // long",
+                   getLLVMStyleWithColumns(15)));
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n"
+            "pt c;   // long",
+            format("int ab; // line\n"
+                   "int a; // long long\n"
+                   "pt c; // long",
+                   getLLVMStyleWithColumns(15)));
+  EXPECT_EQ("int ab; // line\n"
+            "int a;  // long\n"
+            "        // long\n"
+            "\n"
+            "// long",
+            format("int ab; // line\n"
+                   "int a; // long long\n"
+                   "\n"
+                   "// long",
+                   getLLVMStyleWithColumns(15)));
 }
 } // end namespace
 } // end namespace format