I ran into a similar issue a long time ago, with the GNU assembler in "intel_syntax noprefix" mode. It has an issue where there's syntactic ambiguity that makes it possible to interpret a forward-referenced named constant immediate as a reference to an unknown symbol, if in an instruction that could accept either an immediate or a memory address. The net result is assembling the instruction to have a placeholder memory address (expected to be filled in by the relocated address of the symbol when linked) rather than the expected immediate. Painful to debug.