Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp
+++ lib/Format/Format.cpp
@@ -559,7 +559,7 @@
       Limit -= 2;
 
       unsigned MergedLines = 0;
-      if (MergeShortFunctions) {
+      if (MergeShortFunctions && !I[1]->First->MustBreakBefore) {
         MergedLines = tryMergeSimpleBlock(I + 1, E, Limit);
         // If we managed to merge the block, count the function header, which is
         // on a separate line.
@@ -664,7 +664,7 @@
 
       // 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 +674,7 @@
 
       // 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;
@@ -698,6 +697,8 @@
 
   bool nextTwoLinesFitInto(SmallVectorImpl<AnnotatedLine *>::const_iterator I,
                            unsigned Limit) {
+    if (I[1]->First->MustBreakBefore || I[2]->First->MustBreakBefore)
+      return false;
     return 1 + I[1]->Last->TotalLength + 1 + I[2]->Last->TotalLength <= Limit;
   }
 
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -7361,6 +7361,31 @@
                "}\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\n"
+               "void foobar() { foo(); }\n"
+               "#ifdef _DEBUG\n"
+               "void bar() {}\n"
+               "#else\n"
+               "void bar() { foobar(); }\n"
+               "#endif",
+               BreakBeforeBrace);
 }
 
 TEST_F(FormatTest, AllmanBraceBreaking) {
@@ -7443,6 +7468,31 @@
                "}\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\n"
+               "void foobar() { foo(); }\n"
+               "#ifdef _DEBUG\n"
+               "void bar() {}\n"
+               "#else\n"
+               "void bar() { foobar(); }\n"
+               "#endif",
+               BreakBeforeBrace);
+
   BreakBeforeBrace.ColumnLimit = 19;
   verifyFormat("void f() { int i; }", BreakBeforeBrace);
   BreakBeforeBrace.ColumnLimit = 18;
@@ -7563,6 +7613,31 @@
                "  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\n"
+               "void foobar() { foo(); }\n"
+               "#ifdef _DEBUG\n"
+               "void bar() {}\n"
+               "#else\n"
+               "void bar() { foobar(); }\n"
+               "#endif",
+               GNUBraceStyle);
 }
 TEST_F(FormatTest, CatchExceptionReferenceBinding) {
   verifyFormat("void f() {\n"