diff --git a/public/amtl/am-string.h b/public/amtl/am-string.h
index 1d1b7e2a..074339fa 100644
--- a/public/amtl/am-string.h
+++ b/public/amtl/am-string.h
@@ -55,6 +55,8 @@ class AString
   AString(const AString &other) {
     if (other.length_)
       set(other.chars_, other.length_);
+    else
+     length_ = 0;
   }
   AString(Moveable<AString> other)
     : chars_(other->chars_.take()),
diff --git a/public/amtl/am-vector.h b/public/amtl/am-vector.h
index 2e88cc33..2b0b8feb 100644
--- a/public/amtl/am-vector.h
+++ b/public/amtl/am-vector.h
@@ -187,10 +187,10 @@ class Vector : public AllocPolicy
 
   bool moveUp(size_t at) {
     assert(at < nitems_);
-    if (!growIfNeeded(1))
+    if (!append(Moveable<T>(data_[nitems_ - 1])))
       return false;
-    nitems_++;
-    for (size_t i = nitems_ - 1; i > at; i--)
+
+    for (size_t i = nitems_ - 2; i > at; i--)
       data_[i] = Moveable<T>(data_[i - 1]);
     return true;
   }