diff --git a/vlib/math/big/array_ops.v b/vlib/math/big/array_ops.v
index 3124d23093..bff4c5d450 100644
--- a/vlib/math/big/array_ops.v
+++ b/vlib/math/big/array_ops.v
@@ -69,7 +69,7 @@ fn add_digit_array(operand_a []u32, operand_b []u32, mut sum []u32) {
 
 // Subtracts operand_b from operand_a and stores the difference in storage.
 // It assumes operand_a contains the larger "integer" and that storage is
-// the same size as operand_a
+// the same size as operand_a and is 0
 fn subtract_digit_array(operand_a []u32, operand_b []u32, mut storage []u32) {
 	// Zero length cases
 	if operand_a.len == 0 {
@@ -104,7 +104,7 @@ fn subtract_digit_array(operand_a []u32, operand_b []u32, mut storage []u32) {
 		storage[index] = u32(a_digit - b_digit)
 	}
 
-	if storage.last() == 0 {
+	for storage.len > 0 && storage.last() == 0 {
 		storage.delete_last()
 	}
 }
diff --git a/vlib/math/big/array_ops_test.v b/vlib/math/big/array_ops_test.v
index 1841e1431d..813fe31e9c 100644
--- a/vlib/math/big/array_ops_test.v
+++ b/vlib/math/big/array_ops_test.v
@@ -81,6 +81,14 @@ fn test_subtract_digit_array_03() {
 	assert c == [u32(0), 0, u32(-1), u32(-1), 0, 13]
 }
 
+fn test_subtract_digit_array_04() {
+	a := [u32(0x2), 0x4, 0x5, 0x3]
+	b := [u32(0x0), 0x0, 0x5, 0x3]
+	mut c := []u32{len: a.len}
+	subtract_digit_array(a, b, mut c)
+	assert c == [u32(0x2), 0x4]
+}
+
 fn test_multiply_digit_array_01() {
 	a := [u32(0), 0, 0, 1]
 	b := [u32(0), 0, 1]