diff --git a/src/bigint.rs b/src/bigint.rs
index 51e4df6..376ba0b 100644
--- a/src/bigint.rs
+++ b/src/bigint.rs
@@ -38,18 +38,18 @@ macro_rules! impl_from_smaller {
 #[cfg(target_pointer_width = "16")]
 impl_from_smaller!(u8, u16);
 
-#[cfg(target_pointer_width = "32")]
-impl_from_smaller!(u8, u16, u32);
-
-#[cfg(target_pointer_width = "64")]
-impl_from_smaller!(u8, u16, u32, u64);
-
 #[cfg(target_pointer_width = "16")]
 static BITS:usize = 16;
 
+#[cfg(target_pointer_width = "32")]
+impl_from_smaller!(u8, u16, u32);
+
 #[cfg(target_pointer_width = "32")]
 static BITS:usize = 32;
 
+#[cfg(target_pointer_width = "64")]
+impl_from_smaller!(u8, u16, u32, u64);
+
 #[cfg(target_pointer_width = "64")]
 static BITS:usize = 64;
 
@@ -78,7 +78,7 @@ fn add(u: BigInt, v: BigInt) -> BigInt {
             } else {
                 out.inner.push(res);
             }
-            carry = core::usize::MAX - res + 1;
+            carry = core::usize::MAX - res;
         } else {
             if res < core::usize::MAX {
                 out.inner.push(res + carry);
@@ -134,18 +134,7 @@ impl BigInt {
         todo!();
     }
 
-    pub fn from_str_radix() {
-        todo!();
-    }
-
-    /// Split an unsigned number into BigInt parts
-    fn split<T: Unsigned>(&mut self, num: T) -> Vec<usize> {
-        // Pretty easy if you don't actually need to split the value!
-        if num < T::max_value() {
-            todo!();
-            // return vec![num as usize];
-        }
-
+    pub fn from_str_radix<T: ToString>(s: T, radix: usize) {
         todo!();
     }
 }
@@ -160,13 +149,20 @@ mod tests {
         assert_eq!(int.inner[0], 45usize)
     }
 
-    /* #[test]
+    #[test]
     fn test_add() {
-        let a = BigInt::from(core::u64::MAX);
-        let b = BigInt::from(core::u64::MAX);
+        // MAX is 2^Bitsize - 1,
+        // so the sum should be
+        // [MAX -1, 1]
+        // Compare base 10: 9 + 9 = 18
+        let a = BigInt::from(core::usize::MAX);
+        let b = BigInt::from(core::usize::MAX);
 
         let sum = add(a, b);
 
-        assert!(false, "{:#?} should have inner equal to {:?}", sum, core::u64::MAX as u128 + core::u64::MAX as u128);
-    } */
+        assert_eq!(sum.inner[0], core::usize::MAX - 1, "least significant place should be MAX - 1");
+        assert_eq!(sum.inner[1], 1usize, "most significant place should be 1");
+
+        // assert!(false, "{:#?} should have inner equal to {:?}", sum, core::u64::MAX as u128 + core::u64::MAX as u128);
+    }
 }