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
@@ -310,8 +310,13 @@
       // If faced with "a.operator*(argument)" or "a->operator*(argument)",
       // i.e. the operator is called as a member function,
       // then the argument must be an expression.
+      // If faced with "operator+(argument)", i.e. the operator is called as
+      // a free function, then the argument is an expression only if the current
+      // line can't be a declaration.
       bool OperatorCalledAsMemberFunction =
-          Prev->Previous && Prev->Previous->isOneOf(tok::period, tok::arrow);
+          (Prev->Previous &&
+           Prev->Previous->isOneOf(tok::period, tok::arrow)) ||
+          (!Line.MustBeDeclaration && !Line.InMacroBody);
       Contexts.back().IsExpression = OperatorCalledAsMemberFunction;
     } else if (OpeningParen.is(TT_VerilogInstancePortLParen)) {
       Contexts.back().IsExpression = true;
diff --git a/clang/unittests/Format/TokenAnnotatorTest.cpp b/clang/unittests/Format/TokenAnnotatorTest.cpp
--- a/clang/unittests/Format/TokenAnnotatorTest.cpp
+++ b/clang/unittests/Format/TokenAnnotatorTest.cpp
@@ -657,6 +657,33 @@
   EXPECT_TOKEN(Tokens[2], tok::l_paren, TT_OverloadedOperator);
   EXPECT_TOKEN(Tokens[3], tok::r_paren, TT_OverloadedOperator);
   EXPECT_TOKEN(Tokens[4], tok::l_paren, TT_OverloadedOperatorLParen);
+
+  Tokens = annotate("class Foo {\n"
+                    "  int operator+(a* b);\n"
+                    "}");
+  ASSERT_EQ(Tokens.size(), 14u) << Tokens;
+  EXPECT_TOKEN(Tokens[4], tok::kw_operator, TT_FunctionDeclarationName);
+  EXPECT_TOKEN(Tokens[5], tok::plus, TT_OverloadedOperator);
+  EXPECT_TOKEN(Tokens[6], tok::l_paren, TT_OverloadedOperatorLParen);
+  EXPECT_TOKEN(Tokens[8], tok::star, TT_PointerOrReference);
+
+  Tokens = annotate("void foo() {\n"
+                    "  operator+(a * b);\n"
+                    "}");
+  ASSERT_EQ(Tokens.size(), 15u) << Tokens;
+  EXPECT_TOKEN(Tokens[6], tok::plus, TT_OverloadedOperator);
+  EXPECT_TOKEN(Tokens[7], tok::l_paren, TT_OverloadedOperatorLParen);
+  EXPECT_TOKEN(Tokens[9], tok::star, TT_BinaryOperator);
+
+  Tokens = annotate("class Foo {\n"
+                    "  void foo() {\n"
+                    "    operator+(a * b);\n"
+                    "  }\n"
+                    "}");
+  ASSERT_EQ(Tokens.size(), 19u) << Tokens;
+  EXPECT_TOKEN(Tokens[9], tok::plus, TT_OverloadedOperator);
+  EXPECT_TOKEN(Tokens[10], tok::l_paren, TT_OverloadedOperatorLParen);
+  EXPECT_TOKEN(Tokens[12], tok::star, TT_BinaryOperator);
 }
 
 TEST_F(TokenAnnotatorTest, OverloadedOperatorInTemplate) {