diff --git a/example/fibonacci_heap.cpp b/example/fibonacci_heap.cpp
index ffa42ab5..ca70367d 100644
--- a/example/fibonacci_heap.cpp
+++ b/example/fibonacci_heap.cpp
@@ -34,7 +34,7 @@ int main()
         uniform_int<> distrib(0, N - 1);
         boost::variate_generator< random_ns::mt19937&, uniform_int<> > rand_gen(
             gen, distrib);
-        for (int t = 0; t < 10; ++t)
+        for (std::size_t t = 0; t < 10; ++t)
         {
             std::vector< float > v, w(N);
 
diff --git a/example/prim-telephone.cpp b/example/prim-telephone.cpp
index 1f256db0..40b05fc1 100644
--- a/example/prim-telephone.cpp
+++ b/example/prim-telephone.cpp
@@ -53,12 +53,12 @@ int main()
 #endif
 
     int total_weight = 0;
-    for (int v = 0; v < num_vertices(g); ++v)
+    for (std::size_t v = 0; v < num_vertices(g); ++v)
         if (parent[v] != v)
             total_weight += get(weight, edge(parent[v], v, g).first);
     std::cout << "total weight: " << total_weight << std::endl;
 
-    for (int u = 0; u < num_vertices(g); ++u)
+    for (std::size_t u = 0; u < num_vertices(g); ++u)
         if (parent[u] != u)
             edge_attr_map[edge(parent[u], u, g_dot).first]["color"] = "black";
     std::ofstream out("figs/telephone-mst-prim.dot");