diff --git a/peerconnection/samples/server/peer_channel.cc b/peerconnection/samples/server/peer_channel.cc
index d2481a6a2..3d4dbff25 100644
--- a/peerconnection/samples/server/peer_channel.cc
+++ b/peerconnection/samples/server/peer_channel.cc
@@ -228,8 +228,8 @@ bool PeerChannel::AddMember(DataSocket* ds) {
   HandleDeliveryFailures(&failures);
   members_.push_back(new_guy);
 
-  printf("New member added (total=%zu): %s\n",
-      members_.size(), new_guy->name().c_str());
+  printf("New member added (total=%s): %s\n",
+      size_t2str(members_.size()).c_str(), new_guy->name().c_str());
 
   // Let the newly connected peer know about other members of the channel.
   std::string content_type;
@@ -261,7 +261,7 @@ void PeerChannel::OnClosing(DataSocket* ds) {
         break;
     }
   }
-  printf("Total connected: %zu\n", members_.size());
+  printf("Total connected: %s\n", size_t2str(members_.size()).c_str());
 }
 
 void PeerChannel::CheckForTimeout() {
diff --git a/peerconnection/samples/server/utils.cc b/peerconnection/samples/server/utils.cc
index 7cdd045b5..2f0d9f7a6 100644
--- a/peerconnection/samples/server/utils.cc
+++ b/peerconnection/samples/server/utils.cc
@@ -17,3 +17,14 @@ std::string int2str(int i) {
   sprintf(buffer, "%d", i);  // NOLINT
   return buffer;
 }
+
+std::string size_t2str(size_t i) {
+  char buffer[32] = {0};
+#ifdef WIN32
+  // %zu isn't supported on Windows.
+  sprintf(buffer, "%Iu", i);  // NOLINT
+#else
+  sprintf(buffer, "%zu", i);  // NOLINT
+#endif
+  return buffer;
+}
diff --git a/peerconnection/samples/server/utils.h b/peerconnection/samples/server/utils.h
index 74672d337..81b870676 100644
--- a/peerconnection/samples/server/utils.h
+++ b/peerconnection/samples/server/utils.h
@@ -18,5 +18,6 @@
 #endif
 
 std::string int2str(int i);
+std::string size_t2str(size_t i);
 
 #endif  // PEERCONNECTION_SAMPLES_SERVER_UTILS_H_