2 files changed, 13 insertions, 1 deletions
diff --git a/gnuradio-runtime/include/gnuradio/tagged_stream_block.h b/gnuradio-runtime/include/gnuradio/tagged_stream_block.h
index 1fe92ee25a..86343f281d 100644
--- a/gnuradio-runtime/include/gnuradio/tagged_stream_block.h
+++ b/gnuradio-runtime/include/gnuradio/tagged_stream_block.h
@@ -97,6 +97,8 @@ namespace gr {
      */
     void /* final */ forecast (int noutput_items, gr_vector_int &ninput_items_required);
 
+    bool check_topology(int ninputs, int /* noutputs */);
+
     /*!
      * - Reads the number of input items from the tags using parse_length_tags()
      * - Checks there's enough data on the input and output buffers
diff --git a/gnuradio-runtime/lib/tagged_stream_block.cc b/gnuradio-runtime/lib/tagged_stream_block.cc
index c6d5fc1fec..252a235fbf 100644
--- a/gnuradio-runtime/lib/tagged_stream_block.cc
+++ b/gnuradio-runtime/lib/tagged_stream_block.cc
@@ -89,6 +89,14 @@ namespace gr {
     return;
   }
 
+  bool
+  tagged_stream_block::check_topology(int ninputs, int /* noutputs */)
+  {
+    d_n_input_items_reqd.resize(ninputs, 0);
+    return true;
+  }
+
+
   int
   tagged_stream_block::general_work(int noutput_items,
                                     gr_vector_int &ninput_items,
@@ -99,7 +107,9 @@ namespace gr {
       return work(noutput_items, ninput_items, input_items, output_items);
     }
 
-    if(d_n_input_items_reqd[0] == 0) { // Otherwise, it's already set from a previous call
+    // Read TSB tags, unless we...
+    // ...don't have inputs or ...     ... we already set it in a previous run.
+    if(!d_n_input_items_reqd.empty() && d_n_input_items_reqd[0] == 0) {
       std::vector<std::vector<tag_t> > tags(input_items.size(), std::vector<tag_t>());
       for(unsigned i = 0; i < input_items.size(); i++) {
         get_tags_in_range(tags[i], i, nitems_read(i), nitems_read(i)+1);