diff --git a/lib/std/math/bigint.c3 b/lib/std/math/bigint.c3
index 79462a27d..8c6fb83e5 100644
--- a/lib/std/math/bigint.c3
+++ b/lib/std/math/bigint.c3
@@ -44,17 +44,16 @@ fn BigInt* BigInt.init(&self, int128 value)
 fn BigInt* BigInt.init_with_u128(&self, uint128 value)
 {
 	self.data[..] = 0;
-	int128 tmp = value;
+	uint128 tmp = value;
 	uint len = 0;
-	while (tmp != 0 && len < MAX_LEN)
+	while (tmp != 0)
 	{
 		self.data[len] = (uint)(tmp & 0xFFFFFFFF);
 		tmp >>= 32;
 		len++;
 	}
-	self.len = len;
-	assert(value == 0 || tmp == 0 || !self.is_negative());
-	self.len = max(len, 1);
+	assert(!self.is_negative());
+	self.len = max(len ?: 1);
 	return self;
 }
 
@@ -68,7 +67,7 @@ fn BigInt* BigInt.init_with_array(&self, uint[] values)
 
 	foreach_r(i, val : values)
 	{
-		values[values.len - 1 - i] = val;
+		self.data[values.len - 1 - i] = val;
 	}
 	while (self.len > 1 && self.data[self.len - 1] == 0)
 	{