Grammar-based fuzzing has been shown to significantly improve bug detection in programs with highly structured inputs. However, since grammars are largely handwritten, it is rarely used as a standalone technique in large-spectrum fuzzers as it requires human expertise. To fill this gap, promising techniques begin to emerge to automate the extraction of context-free grammars directly from the program under test. Unfortunately, the resulting grammars are usually not expressive enough and generate too many wrong inputs to provide results capable of competing with other fuzzing techniques. In this paper we propose a technique to automate the creation of attribute grammars from context-free grammars, thus significantly lowering the barrier of entry for efficient and effective large-scale grammar-based fuzzing.