diff --git a/vm/math.hpp b/vm/math.hpp
index d78ae54010..c2444b98f9 100644
--- a/vm/math.hpp
+++ b/vm/math.hpp
@@ -90,8 +90,8 @@ VM_C_API cell from_unsigned_cell(cell integer, factor_vm *vm);
 VM_C_API cell from_signed_8(s64 n, factor_vm *vm);
 VM_C_API cell from_unsigned_8(u64 n, factor_vm *vm);
 
-VM_C_API s64 to_signed_8(cell obj, factor_vm *vm);
-VM_C_API u64 to_unsigned_8(cell obj, factor_vm *vm);
+VM_C_API s64 *to_signed_8(cell obj, factor_vm *vm);
+VM_C_API s64 *to_unsigned_8(cell obj, factor_vm *vm);
 
 VM_C_API fixnum to_fixnum(cell tagged, factor_vm *vm);
 VM_C_API cell to_cell(cell tagged, factor_vm *vm);