Index: lib/Format/UnwrappedLineParser.cpp
===================================================================
--- lib/Format/UnwrappedLineParser.cpp
+++ lib/Format/UnwrappedLineParser.cpp
@@ -1367,7 +1367,8 @@
 
   const FormatToken &InitialToken = *FormatTok;
   nextToken();
-  if (FormatTok->Tok.is(tok::identifier))
+  while (FormatTok->Tok.is(tok::identifier) ||
+         FormatTok->Tok.is(tok::coloncolon))
     nextToken();
   if (FormatTok->Tok.is(tok::l_brace)) {
     if (ShouldBreakBeforeBrace(Style, InitialToken))
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -2192,6 +2192,13 @@
                    "}    // my_namespace\n"
                    "#endif    // HEADER_GUARD"));
 
+  EXPECT_EQ("namespace A::B {\n"
+            "class C {};\n"
+            "}",
+            format("namespace A::B {\n"
+                   "class C {};\n"
+                   "}"));
+
   FormatStyle Style = getLLVMStyle();
   Style.NamespaceIndentation = FormatStyle::NI_All;
   EXPECT_EQ("namespace out {\n"