1 files changed, 12 insertions, 0 deletions
diff --git a/gnuradio-core/src/lib/runtime/gr_hier_block2_detail.cc b/gnuradio-core/src/lib/runtime/gr_hier_block2_detail.cc
index a026851d2..e5336d483 100644
--- a/gnuradio-core/src/lib/runtime/gr_hier_block2_detail.cc
+++ b/gnuradio-core/src/lib/runtime/gr_hier_block2_detail.cc
@@ -267,6 +267,12 @@ gr_hier_block2_detail::resolve_port(int port, bool is_input)
       throw std::runtime_error(msg.str());
     }
 
+    if (d_inputs[port] == gr_endpoint()) {
+      msg << "hierarchical block '" << d_owner->name() << "' input " << port
+	  << " is not connected internally";
+      throw std::runtime_error(msg.str());
+    }
+
     result = resolve_endpoint(d_inputs[port], true);
   }
   else {
@@ -275,6 +281,12 @@ gr_hier_block2_detail::resolve_port(int port, bool is_input)
       throw std::runtime_error(msg.str());
     }
 
+    if (d_outputs[port] == gr_endpoint()) {
+      msg << "hierarchical block '" << d_owner->name() << "' output " << port
+	  << " is not connected internally";
+      throw std::runtime_error(msg.str());
+    }
+
     result = resolve_endpoint(d_outputs[port], false);
   }