diff --git a/doc/rippled-example.cfg b/doc/rippled-example.cfg
index 9f1eaee217..97a6bc61f4 100644
--- a/doc/rippled-example.cfg
+++ b/doc/rippled-example.cfg
@@ -303,8 +303,8 @@
 #   Ripple network through a public-facing server, or for building a set
 #   of cluster peers.
 #
-#   One IPv4 address or domain names per line is allowed. A port may optionally
-#   be specified after adding a space to the address.
+#   One IPv4 address or domain names per line is allowed. A port must be
+#   specified after adding a space to the address.
 #
 #
 #
diff --git a/src/ripple/peerfinder/impl/Logic.h b/src/ripple/peerfinder/impl/Logic.h
index a07ff7e85b..e3eac66203 100644
--- a/src/ripple/peerfinder/impl/Logic.h
+++ b/src/ripple/peerfinder/impl/Logic.h
@@ -211,6 +211,12 @@ public:
 
         for (auto const& remote_address : addresses)
         {
+            if (remote_address.port () == 0)
+            {
+                throw std::runtime_error ("Port not specified for address:" +
+                    remote_address.to_string ());
+            }
+
             auto result (state->fixed.emplace (std::piecewise_construct,
                 std::forward_as_tuple (remote_address),
                     std::make_tuple (std::ref (m_clock))));