diff --git a/clang/lib/Format/UnwrappedLineFormatter.h b/clang/lib/Format/UnwrappedLineFormatter.h
--- a/clang/lib/Format/UnwrappedLineFormatter.h
+++ b/clang/lib/Format/UnwrappedLineFormatter.h
@@ -47,6 +47,7 @@
   /// of the \c UnwrappedLine if there was no structural parsing error.
   void formatFirstToken(const AnnotatedLine &Line,
                         const AnnotatedLine *PreviousLine,
+                        const AnnotatedLine *PrevPrevLine,
                         const SmallVectorImpl<AnnotatedLine *> &Lines,
                         unsigned Indent, unsigned NewlineIndent);
 
diff --git a/clang/lib/Format/UnwrappedLineFormatter.cpp b/clang/lib/Format/UnwrappedLineFormatter.cpp
--- a/clang/lib/Format/UnwrappedLineFormatter.cpp
+++ b/clang/lib/Format/UnwrappedLineFormatter.cpp
@@ -1134,6 +1134,7 @@
   unsigned Penalty = 0;
   LevelIndentTracker IndentTracker(Style, Keywords, Lines[0]->Level,
                                    AdditionalIndent);
+  const AnnotatedLine *PrevPrevLine = nullptr;
   const AnnotatedLine *PreviousLine = nullptr;
   const AnnotatedLine *NextLine = nullptr;
 
@@ -1172,7 +1173,7 @@
     if (ShouldFormat && TheLine.Type != LT_Invalid) {
       if (!DryRun) {
         bool LastLine = Line->First->is(tok::eof);
-        formatFirstToken(TheLine, PreviousLine, Lines, Indent,
+        formatFirstToken(TheLine, PreviousLine, PrevPrevLine, Lines, Indent,
                          LastLine ? LastStartColumn : NextStartColumn + Indent);
       }
 
@@ -1218,7 +1219,7 @@
                               TheLine.LeadingEmptyLinesAffected);
         // Format the first token.
         if (ReformatLeadingWhitespace)
-          formatFirstToken(TheLine, PreviousLine, Lines,
+          formatFirstToken(TheLine, PreviousLine, PrevPrevLine, Lines,
                            TheLine.First->OriginalColumn,
                            TheLine.First->OriginalColumn);
         else
@@ -1234,6 +1235,7 @@
     }
     if (!DryRun)
       markFinalized(TheLine.First);
+    PrevPrevLine = PreviousLine;
     PreviousLine = &TheLine;
   }
   PenaltyCache[CacheKey] = Penalty;
@@ -1242,6 +1244,7 @@
 
 void UnwrappedLineFormatter::formatFirstToken(
     const AnnotatedLine &Line, const AnnotatedLine *PreviousLine,
+    const AnnotatedLine *PrevPrevLine,
     const SmallVectorImpl<AnnotatedLine *> &Lines, unsigned Indent,
     unsigned NewlineIndent) {
   FormatToken &RootToken = *Line.First;
@@ -1273,6 +1276,8 @@
   if (!Style.KeepEmptyLinesAtTheStartOfBlocks && PreviousLine &&
       PreviousLine->Last->is(tok::l_brace) &&
       !PreviousLine->startsWithNamespace() &&
+      !(PrevPrevLine && PrevPrevLine->startsWithNamespace() &&
+        PreviousLine->startsWith(tok::l_brace)) &&
       !startsExternCBlock(*PreviousLine))
     Newlines = 1;
 
diff --git a/clang/unittests/Format/FormatTest.cpp b/clang/unittests/Format/FormatTest.cpp
--- a/clang/unittests/Format/FormatTest.cpp
+++ b/clang/unittests/Format/FormatTest.cpp
@@ -262,6 +262,128 @@
                    "}",
                    getGoogleStyle()));
 
+  auto CustomStyle = clang::format::getLLVMStyle();
+  CustomStyle.BreakBeforeBraces = clang::format::FormatStyle::BS_Custom;
+  CustomStyle.BraceWrapping.AfterNamespace = true;
+  CustomStyle.KeepEmptyLinesAtTheStartOfBlocks = false;
+  EXPECT_EQ("namespace N\n"
+            "{\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("namespace N\n"
+                   "{\n"
+                   "\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   CustomStyle));
+  EXPECT_EQ("/* something */ namespace N\n"
+            "{\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("/* something */ namespace N {\n"
+                   "\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   CustomStyle));
+  EXPECT_EQ("inline namespace N\n"
+            "{\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("inline namespace N\n"
+                   "{\n"
+                   "\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   CustomStyle));
+  EXPECT_EQ("/* something */ inline namespace N\n"
+            "{\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("/* something */ inline namespace N\n"
+                   "{\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   CustomStyle));
+  EXPECT_EQ("export namespace N\n"
+            "{\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("export namespace N\n"
+                   "{\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   CustomStyle));
+  EXPECT_EQ("namespace a\n"
+            "{\n"
+            "namespace b\n"
+            "{\n"
+            "\n"
+            "class AA {};\n"
+            "\n"
+            "} // namespace b\n"
+            "} // namespace a\n",
+            format("namespace a\n"
+                   "{\n"
+                   "namespace b\n"
+                   "{\n"
+                   "\n"
+                   "\n"
+                   "class AA {};\n"
+                   "\n"
+                   "\n"
+                   "}\n"
+                   "}\n",
+                   CustomStyle));
+  EXPECT_EQ("namespace A /* comment */\n"
+            "{\n"
+            "class B {}\n"
+            "} // namespace A",
+            format("namespace A /* comment */ { class B {} }", CustomStyle));
+  EXPECT_EQ("namespace A\n"
+            "{ /* comment */\n"
+            "class B {}\n"
+            "} // namespace A",
+            format("namespace A {/* comment */ class B {} }", CustomStyle));
+  EXPECT_EQ("namespace A\n"
+            "{ /* comment */\n"
+            "\n"
+            "class B {}\n"
+            "\n"
+            ""
+            "} // namespace A",
+            format("namespace A { /* comment */\n"
+                   "\n"
+                   "\n"
+                   "class B {}\n"
+                   "\n"
+                   "\n"
+                   "}",
+                   CustomStyle));
+  EXPECT_EQ("namespace A /* comment */\n"
+            "{\n"
+            "\n"
+            "class B {}\n"
+            "\n"
+            "} // namespace A",
+            format("namespace A/* comment */ {\n"
+                   "\n"
+                   "\n"
+                   "class B {}\n"
+                   "\n"
+                   "\n"
+                   "}",
+                   CustomStyle));
+
   // ...but do keep inlining and removing empty lines for non-block extern "C"
   // functions.
   verifyFormat("extern \"C\" int f() { return 42; }", getGoogleStyle());