diff --git a/compiler2/map.hh b/compiler2/map.hh
index fdc01c43565abe9cd71a7d70e426138208146d07..532bfb23ba91c38e1f26c81f8994f49c2e1f91c9 100644
--- a/compiler2/map.hh
+++ b/compiler2/map.hh
@@ -81,7 +81,7 @@ private:
 
 public:
 
-  static const size_t max_map_length = -1;
+  static const size_t max_map_length = (size_t) -1;
 
   /** Creates an empty map. */
   map() : num_m(0), max_m(0), last_searched_key(0), m_ptr(NULL) { }
diff --git a/compiler2/vector.hh b/compiler2/vector.hh
index fd977d806a8171b22bf7993cab287cec7e9415d7..b38f6680c32fb181ff1519e37f8e3e549ef41085 100644
--- a/compiler2/vector.hh
+++ b/compiler2/vector.hh
@@ -67,7 +67,7 @@ private:
 
 public:
 
-  static const size_t max_vector_length = -1;
+  static const size_t max_vector_length = (size_t) -1;
 
   /** Creates an empty vector. */
   vector() : num_e(0), e_ptr(NULL) { }