diff --git a/src/A3t.cpp b/src/A3t.cpp
index 4d5e1bdf8..9fef6a42c 100644
--- a/src/A3t.cpp
+++ b/src/A3t.cpp
@@ -76,6 +76,16 @@ void A3t::initialize (int argc, const char** argv)
   }
 }
 
+////////////////////////////////////////////////////////////////////////////////
+void A3t::clear ()
+{
+  delete _tree;
+
+  _tree = new Tree ("root");
+  if (! _tree)
+    throw std::string ("Failed to allocate memory for parse tree.");
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 // Add an arg for every word from std::cin.
 //
@@ -514,11 +524,12 @@ Tree* A3t::captureFirst (const std::string& arg)
   t->_trunk = _tree;
 
   std::vector <Tree*>::iterator i = _tree->_branches.begin ();
-  i++;  // Walk past the binary.
+  if (i != _tree->_branches.end ())
+    i++;  // Walk past the binary.
 
   _tree->_branches.insert (i, t);
-  findCommand ();
 
+  findCommand ();
   return t;
 }
 
diff --git a/src/A3t.h b/src/A3t.h
index b92a9231e..8a050890b 100644
--- a/src/A3t.h
+++ b/src/A3t.h
@@ -38,6 +38,7 @@ public:
   A3t ();
   ~A3t ();
   void initialize (int, const char**);
+  void clear ();
   void appendStdin ();
   Tree* tree ();
   Tree* parse ();