diff --git a/factor/factor.rs b/factor/factor.rs
index 5d78cab0e..fcb87bb95 100644
--- a/factor/factor.rs
+++ b/factor/factor.rs
@@ -27,6 +27,9 @@ static NAME: &'static str = "factor";
 fn factor(mut num: u64) -> Vec<u64> {
     let mut ret = Vec::new();
 
+    if num < 2 {
+        return ret;
+    }
     while num % 2 == 0 {
         num /= 2;
         ret.push(2);
diff --git a/md5sum/rust-crypto b/md5sum/rust-crypto
index adde85617..1711f3a64 160000
--- a/md5sum/rust-crypto
+++ b/md5sum/rust-crypto
@@ -1 +1 @@
-Subproject commit adde85617a776ea98249504d653cb547a2353c98
+Subproject commit 1711f3a648a5ee1519963820f742b28693c1ce6d