diff --git a/src/Statement.cc b/src/Statement.cc
index dcec55979be9bf8359354c1cba981587ac724191..ee1ecadf09e525f4c3ce15fab9a32089dc6bdb68 100644
--- a/src/Statement.cc
+++ b/src/Statement.cc
@@ -310,7 +310,7 @@ OptionsList::writeJsonOutput(ostream &output) const
   for (auto it = paired_num_options.begin();
        it != paired_num_options.end();)
     {
-      output << R"(")"<< it->first << R"(": [)" << it->second.first << " " << it->second.second << "]";
+      output << R"(")"<< it->first << R"(": [)" << it->second.first << ", " << it->second.second << "]";
       ++it;
       if (it != paired_num_options.end()
           || !(string_options.empty()