diff --git a/clang/lib/Format/TokenAnnotator.cpp b/clang/lib/Format/TokenAnnotator.cpp
--- a/clang/lib/Format/TokenAnnotator.cpp
+++ b/clang/lib/Format/TokenAnnotator.cpp
@@ -1337,11 +1337,11 @@
     if (CurrentToken &&
         CurrentToken->isOneOf(Keywords.kw_mark, Keywords.kw_option,
                               Keywords.kw_region)) {
-      bool IsMark = CurrentToken->is(Keywords.kw_mark);
+      bool IsMarkOrRegion = CurrentToken->isOneOf(Keywords.kw_mark, Keywords.kw_region);
       next();
       next(); // Consume first token (so we fix leading whitespace).
       while (CurrentToken) {
-        if (IsMark || CurrentToken->Previous->is(TT_BinaryOperator))
+        if (IsMarkOrRegion || CurrentToken->Previous->is(TT_BinaryOperator))
           CurrentToken->setType(TT_ImplicitStringLiteral);
         next();
       }
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
@@ -19968,6 +19968,11 @@
 
   EXPECT_EQ("#pragma region TEST(FOO : BAR)",
             format("#pragma region TEST(FOO : BAR)", Style));
+
+  verifyFormat("#pragma region TEST(FOO: NOSPACE)", Style);
+  EXPECT_EQ("#pragma region TEST(FOO: NOSPACE)",
+            format("#pragma region TEST(FOO: NOSPACE)", Style));
+
 }
 
 TEST_F(FormatTest, OptimizeBreakPenaltyVsExcess) {