diff --git a/include/chibi/sexp.h b/include/chibi/sexp.h
index fb86945d..c66ca17d 100755
--- a/include/chibi/sexp.h
+++ b/include/chibi/sexp.h
@@ -1085,7 +1085,7 @@ SEXP_API sexp sexp_make_unsigned_integer(sexp ctx, sexp_luint_t x);
 #define sexp_context_exception(x) (sexp_vector_ref(sexp_context_specific(x), SEXP_SIX))
 
 #if SEXP_USE_ALIGNED_BYTECODE
-#define sexp_context_align_pos(ctx) sexp_context_pos(ctx) = (sexp)sexp_word_align((sexp_uint_t)sexp_context_pos(ctx))
+#define sexp_context_align_pos(ctx) sexp_context_pos(ctx) = (sexp)sexp_make_fixnum(sexp_word_align((sexp_uint_t)sexp_unbox_fixnum(sexp_context_pos(ctx))))
 #else
 #define sexp_context_align_pos(ctx)
 #endif