diff --git a/py/objint.c b/py/objint.c
index db8eaa48d8fa574efd96dfee70f166e35b2d06a1..57fe364dcfd0a97b462ea9605442bff51eac06d0 100644
--- a/py/objint.c
+++ b/py/objint.c
@@ -107,7 +107,9 @@ mp_fp_as_int_class_t mp_classify_fp_as_int(mp_float_t val) {
     } else {
         e &= ~((1 << MP_FLOAT_EXP_SHIFT_I32) - 1);
     }
-    if (e <= ((BITS_PER_WORD + MP_FLOAT_EXP_BIAS - 3) << MP_FLOAT_EXP_SHIFT_I32)) {
+    // 8 * sizeof(uintptr_t) counts the number of bits for a small int
+    // TODO provide a way to configure this properly
+    if (e <= ((8 * sizeof(uintptr_t) + MP_FLOAT_EXP_BIAS - 3) << MP_FLOAT_EXP_SHIFT_I32)) {
         return MP_FP_CLASS_FIT_SMALLINT;
     }
 #if MICROPY_LONGINT_IMPL == MICROPY_LONGINT_IMPL_LONGLONG