diff --git a/lib7/std/math/bigint.c3 b/lib7/std/math/bigint.c3
index 768a1f033..ba3267a86 100644
--- a/lib7/std/math/bigint.c3
+++ b/lib7/std/math/bigint.c3
@@ -44,16 +44,15 @@ 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());
+	assert(!self.is_negative());
 	self.len = max(len, 1);
 	return self;
 }
@@ -64,11 +63,18 @@ fn BigInt* BigInt.init_with_u128(&self, uint128 value)
 fn BigInt* BigInt.init_with_array(&self, uint[] values)
 {
 	self.data[..] = 0;
+
+	if (values.len == 0)
+	{
+		self.len = 1;
+		return self;
+	}
+
 	self.len = values.len;
 
 	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)
 	{
diff --git a/test/unit7/stdlib/math/bigint.c3 b/test/unit7/stdlib/math/bigint.c3
index 41b21f718..aa0893446 100644
--- a/test/unit7/stdlib/math/bigint.c3
+++ b/test/unit7/stdlib/math/bigint.c3
@@ -1,5 +1,19 @@
 module std::math::bigint @test;
 
+fn void test_init_with_u128()
+{
+	BigInt bi @noinit;
+	assert(!bi.init_with_u128(uint128.max).is_negative());
+}
+
+fn void init_with_array()
+{
+	BigInt bi @noinit;
+	assert(bi.init_with_array({}).equals(ZERO));
+	assert(bi.init_with_array({0, 0, 0, 1}).equals(bigint::from_int(1)));
+	assert("100000000" == bi.init_with_array({1, 0}).to_string_with_radix(16, allocator::temp()));
+}
+
 fn void test_parse16()
 {
 	BigInt bi @noinit;