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GCC 4.7.2 compiles this: constexpr int i = 5; []{ std::integral_constant< int, i >(); }; // nonstandard: i not captured but not this: constexpr int i = 5; [&i]{ std::integral_constant< int, i >(); }; // GCC says i not constexpr The latter example appears correct to me, according to C++11 §5.1.2/15: An entity is captured by reference if it is implicitly or explicitly captured but not captured by copy. It is unspecified whether additional unnamed non-static data members are declared in the closure type for entities captured by reference. It seems the captured object i inside the lambda refers to the variable in the enclosing scope, which is constexpr , not merely a const reference. The standard explicitly says that the use of a by-value capture is transformed into a use of the corresponding member of the lambda object. And I think that 5.1.2 hints that my interpretation is correct. Is there anything that explicitly says that whether a capture by reference refers to the object in the enclosing scope or a reference?

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