1 files changed, 1 insertions, 0 deletions
diff --git a/decoder/hg_io.cc b/decoder/hg_io.cc
index bfb2fb80..8bd40387 100644
--- a/decoder/hg_io.cc
+++ b/decoder/hg_io.cc
@@ -261,6 +261,7 @@ static void WriteRule(const TRule& r, ostream* out) {
 }
 
 bool HypergraphIO::WriteToJSON(const Hypergraph& hg, bool remove_rules, ostream* out) {
+  if (hg.empty()) { *out << "{}\n"; return true; }
   map<const TRule*, int> rid;
   ostream& o = *out;
   rid[NULL] = 0;