Looks like you encountered a bug. Applying this patch fixes it:
diff --git a/jit/jit-apply.c b/jit/jit-apply.c
index c41993d..2a0b11e 100644
--- a/jit/jit-apply.c
+++ b/jit/jit-apply.c
@@ -191,7 +191,7 @@ jit_apply_builder_add_arguments(jit_apply_builder *builder, jit_type_t signature
case JIT_TYPE_NINT:
case JIT_TYPE_PTR:
case JIT_TYPE_SIGNATURE:
- jit_apply_builder_add_nint(builder, *((jit_nint *) args));
+ jit_apply_builder_add_nint(builder, *((jit_nint *) arg));
break;
case JIT_TYPE_NUINT:
@@ -199,7 +199,7 @@ jit_apply_builder_add_arguments(jit_apply_builder *builder, jit_type_t signature
break;
case JIT_TYPE_LONG:
- jit_apply_builder_add_long(builder, *((jit_long *) args));
+ jit_apply_builder_add_long(builder, *((jit_long *) arg));
break;
case JIT_TYPE_ULONG: