Index: lib/Format/TokenAnnotator.cpp
===================================================================
--- lib/Format/TokenAnnotator.cpp
+++ lib/Format/TokenAnnotator.cpp
@@ -216,6 +216,7 @@
     bool HasMultipleParametersOnALine = false;
     bool MightBeObjCForRangeLoop =
         Left->Previous && Left->Previous->is(tok::kw_for);
+    FormatToken *PossibleObjCForInToken = nullptr;
     while (CurrentToken) {
       // LookForDecls is set when "if (" has been seen. Check for
       // 'identifier' '*' 'identifier' followed by not '=' -- this
@@ -301,10 +302,17 @@
            CurrentToken->Previous->isSimpleTypeSpecifier()) &&
           !CurrentToken->is(tok::l_brace))
         Contexts.back().IsExpression = false;
-      if (CurrentToken->isOneOf(tok::semi, tok::colon))
+      if (CurrentToken->isOneOf(tok::semi, tok::colon)) {
         MightBeObjCForRangeLoop = false;
-      if (MightBeObjCForRangeLoop && CurrentToken->is(Keywords.kw_in))
-        CurrentToken->Type = TT_ObjCForIn;
+        if (PossibleObjCForInToken) {
+          PossibleObjCForInToken->Type = TT_Unknown;
+          PossibleObjCForInToken = nullptr;
+        }
+      }
+      if (MightBeObjCForRangeLoop && CurrentToken->is(Keywords.kw_in)) {
+        PossibleObjCForInToken = CurrentToken;
+        PossibleObjCForInToken->Type = TT_ObjCForIn;
+      }
       // When we discover a 'new', we set CanBeExpression to 'false' in order to
       // parse the type correctly. Reset that after a comma.
       if (CurrentToken->is(tok::comma))
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -775,6 +775,20 @@
                "     aaaaaaaaaaaa.aaaaaaaaaaaa().aaaaaaaaa().a()) {\n}");
 }
 
+TEST_F(FormatTest, ObjCForInLoop) {
+  verifyFormat("for (Foo *x = 0; x != in; x++) {\n}");
+  verifyFormat("for (Foo *x in bar) {\n}");
+  verifyFormat("for (Foo *x in [bar baz]) {\n}");
+  verifyFormat("for (Foo *x in [bar baz:blech]) {\n}");
+  verifyFormat("for (Foo *x in [bar baz:blech, 1, 2, 3, 0]) {\n}");
+  verifyFormat("for (Foo *x in [bar baz:^{\n"
+               "       [uh oh];\n"
+               "     }]) {\n}");
+  verifyFormat("Foo *x;\nfor (x = 0; x != in; x++) {\n}");
+  verifyFormat("Foo *x;\nfor (x in y) {\n}");
+  verifyFormat("for (const Foo<Bar> &baz = in.value(); !baz.at_end(); ++baz) {\n}");
+}
+
 TEST_F(FormatTest, ForEachLoops) {
   verifyFormat("void f() {\n"
                "  foreach (Item *item, itemlist) {}\n"
@@ -12120,6 +12134,31 @@
   EXPECT_EQ(FormatStyle::LK_Cpp, guessLanguage("foo.h", "[[foo::bar, ...]]"));
 }
 
+TEST_F(FormatTest, GuessLanguageWithForIn) {
+  EXPECT_EQ(FormatStyle::LK_Cpp,
+            guessLanguage("foo.h", "for (Foo *x = 0; x != in; x++) {}"));
+  EXPECT_EQ(FormatStyle::LK_ObjC,
+            guessLanguage("foo.h", "for (Foo *x in bar) {}"));
+  EXPECT_EQ(FormatStyle::LK_ObjC,
+            guessLanguage("foo.h", "for (Foo *x in [bar baz]) {}"));
+  EXPECT_EQ(FormatStyle::LK_ObjC,
+            guessLanguage("foo.h", "for (Foo *x in [bar baz:blech]) {}"));
+  EXPECT_EQ(
+      FormatStyle::LK_ObjC,
+      guessLanguage("foo.h", "for (Foo *x in [bar baz:blech, 1, 2, 3, 0]) {}"));
+  EXPECT_EQ(FormatStyle::LK_ObjC,
+            guessLanguage("foo.h", "for (Foo *x in [bar baz:^{[uh oh];}]) {}"));
+  EXPECT_EQ(FormatStyle::LK_Cpp,
+            guessLanguage("foo.h", "Foo *x; for (x = 0; x != in; x++) {}"));
+  EXPECT_EQ(FormatStyle::LK_ObjC,
+            guessLanguage("foo.h", "Foo *x; for (x in y) {}"));
+  EXPECT_EQ(
+      FormatStyle::LK_Cpp,
+      guessLanguage(
+          "foo.h",
+          "for (const Foo<Bar>& baz = in.value(); !baz.at_end(); ++baz) {}"));
+}
+
 } // end namespace
 } // end namespace format
 } // end namespace clang