Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -638,7 +638,8 @@
     // we're not in a control flow statement and the last token is an opening
     // brace.
     AnnotatedLine &Line = **I;
-    if (Line.First->isOneOf(tok::kw_if, tok::kw_while, tok::kw_do, tok::r_brace,
+    if (Line.First->MustBreakBefore ||
+        Line.First->isOneOf(tok::kw_if, tok::kw_while, tok::kw_do, tok::r_brace,
                             tok::kw_else, tok::kw_try, tok::kw_catch,
                             tok::kw_for, tok::kw_case,
                             // This gets rid of all ObjC @ keywords and methods.
@@ -654,9 +655,16 @@
       Tok->CanBreakBefore = true;
       return 1;
     } else if (Limit != 0 && Line.First->isNot(tok::kw_namespace)) {
-      // Check that we still have three lines and they fit into the limit.
+      // Check that we still have three lines
       if (I + 2 == E || I[2]->Type == LT_Invalid)
         return 0;
+
+      // We have already checked for current line. Check if other two lines
+      // allows merging
+      if (I[1]->First->MustBreakBefore || I[2]->First->MustBreakBefore)
+        return 0;
+
+      // Check if they fit into the limit.
       Limit = limitConsideringMacros(I + 2, E, Limit);
 
       if (!nextTwoLinesFitInto(I, Limit))
@@ -664,7 +672,7 @@
 
       // Second, check that the next line does not contain any braces - if it
       // does, readability declines when putting it into a single line.
-      if (I[1]->Last->Type == TT_LineComment || Tok->MustBreakBefore)
+      if (I[1]->Last->Type == TT_LineComment)
         return 0;
       do {
         if (Tok->isOneOf(tok::l_brace, tok::r_brace))
@@ -674,8 +682,7 @@
 
       // Last, check that the third line contains a single closing brace.
       Tok = I[2]->First;
-      if (Tok->getNextNonComment() != NULL || Tok->isNot(tok::r_brace) ||
-          Tok->MustBreakBefore)
+      if (Tok->getNextNonComment() != NULL || Tok->isNot(tok::r_brace))
         return 0;
 
       return 2;
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -7336,6 +7336,25 @@
                "}\n"
                "}",
                BreakBeforeBrace);
+
+  verifyFormat("#ifdef _DEBUG\n"
+               "int foo(int i = 0)\n"
+               "#else\n"
+               "int foo(int i = 5)\n"
+               "#endif\n"
+               "{\n"
+               "  return i;\n"
+               "}\n"
+               "void foo1()\n"
+               "#ifdef _DEBUG\n"
+               "{\n"
+               "  foo();\n"
+               "}\n"
+               "#else\n"
+               "{\n"
+               "}\n"
+               "#endif",
+               BreakBeforeBrace);
 }
 
 TEST_F(FormatTest, AllmanBraceBreaking) {
@@ -7418,6 +7437,25 @@
                "}\n",
                BreakBeforeBrace);
 
+  verifyFormat("#ifdef _DEBUG\n"
+               "int foo(int i = 0)\n"
+               "#else\n"
+               "int foo(int i = 5)\n"
+               "#endif\n"
+               "{\n"
+               "  return i;\n"
+               "}\n"
+               "void foo1()\n"
+               "#ifdef _DEBUG\n"
+               "{\n"
+               "  foo();\n"
+               "}\n"
+               "#else\n"
+               "{\n"
+               "}\n"
+               "#endif",
+               BreakBeforeBrace);
+
   BreakBeforeBrace.ColumnLimit = 19;
   verifyFormat("void f() { int i; }", BreakBeforeBrace);
   BreakBeforeBrace.ColumnLimit = 18;
@@ -7538,6 +7576,25 @@
                "  Y = 0,\n"
                "}\n",
                GNUBraceStyle);
+
+  verifyFormat("#ifdef _DEBUG\n"
+               "int foo(int i = 0)\n"
+               "#else\n"
+               "int foo(int i = 5)\n"
+               "#endif\n"
+               "{\n"
+               "  return i;\n"
+               "}\n"
+               "void foo1()\n"
+               "#ifdef _DEBUG\n"
+               "{\n"
+               "  foo();\n"
+               "}\n"
+               "#else\n"
+               "{\n"
+               "}\n"
+               "#endif",
+               GNUBraceStyle);
 }
 TEST_F(FormatTest, CatchExceptionReferenceBinding) {
   verifyFormat("void f() {\n"