The GitHub issue at https://github.com/froydnj/ironclad/issues/76 doesn't mention it explicitly, but I suspect that the upstream commit that fixes the problem is https://github.com/sbcl/sbcl/commit/86a0d4b23b0a03c09947c06e5c7bdf770f34821a . The commit following that one, https://github.com/sbcl/sbcl/commit/cda85b7a791a1d1958b78d84d32e11b6ff297609 , seems to have some ARM test fixes. Not sure if those are relevant.