diff --git a/src/Val.cc b/src/Val.cc
index 2da784de9b..a6958b35b5 100644
--- a/src/Val.cc
+++ b/src/Val.cc
@@ -494,8 +494,8 @@ static ZeekJson BuildJSON(Val* val, bool only_loggable=false, RE_Matcher* re=new
 		case TYPE_PORT:
 			{
 			auto* pval = val->AsPortVal();
-			j["port"] = pval->Port();
-			j["proto"] = pval->Protocol();
+			j.emplace("port", pval->Port());
+			j.emplace("proto", pval->Protocol());
 			break;
 			}
 
@@ -577,7 +577,7 @@ static ZeekJson BuildJSON(Val* val, bool only_loggable=false, RE_Matcher* re=new
 					else
 						key_string = key_json.dump();
 
-					j[key_string] = BuildJSON(entry_value, only_loggable, re);
+					j.emplace(key_string, BuildJSON(entry_value, only_loggable, re));
 					}
 
 				Unref(lv);
@@ -614,7 +614,7 @@ static ZeekJson BuildJSON(Val* val, bool only_loggable=false, RE_Matcher* re=new
 				Val* value = key_field->Lookup("value", true);
 
 				if ( value && ( ! only_loggable || key_field->Lookup("log")->AsBool() ) )
-					j[key_string] = BuildJSON(value, only_loggable, re);
+					j.emplace(key_string, BuildJSON(value, only_loggable, re));
 				}
 
 			delete fields;
@@ -646,9 +646,8 @@ static ZeekJson BuildJSON(Val* val, bool only_loggable=false, RE_Matcher* re=new
 
 		case TYPE_OPAQUE:
 			{
-			j = ZeekJson::object();
 			auto* oval = val->AsOpaqueVal();
-			j["opaque_type"] = OpaqueMgr::mgr()->TypeID(oval);
+			j = { { "opaque_type", OpaqueMgr::mgr()->TypeID(oval) } };
 			break;
 			}
 
diff --git a/src/threading/formatters/JSON.cc b/src/threading/formatters/JSON.cc
index 58b1ffd779..096e823a10 100644
--- a/src/threading/formatters/JSON.cc
+++ b/src/threading/formatters/JSON.cc
@@ -37,7 +37,7 @@ bool JSON::Describe(ODesc* desc, int num_fields, const Field* const * fields,
 			if ( new_entry.is_null() )
 				return false;
 
-			j[fields[i]->name] = new_entry;
+			j.emplace(fields[i]->name, new_entry);
 			}
 		}
 
@@ -182,11 +182,7 @@ ZeekJson JSON::BuildJSON(Value* val, const string& name) const
 		}
 
 	if ( ! name.empty() && ! j.is_null() )
-		{
-		ZeekJson j2 = ZeekJson::object();
-		j2[name] = j;
-		return j2;
-		}
+		return { { name, j } };
 
 	return j;
 	}
diff --git a/testing/btest/Baseline/scripts.base.utils.json/output b/testing/btest/Baseline/scripts.base.utils.json/output
index 2d2e56253f..3be9649902 100644
--- a/testing/btest/Baseline/scripts.base.utils.json/output
+++ b/testing/btest/Baseline/scripts.base.utils.json/output
@@ -38,3 +38,4 @@ true
 {"10.1.1.1":{"a":1},"10.2.2.2":{"b":2}}
 {"10.1.1.1":[1,2],"10.2.2.2":[3,5]}
 {"1":{"s":"test"}}
+{"opaque_type":"TopkVal"}
diff --git a/testing/btest/scripts/base/utils/json.test b/testing/btest/scripts/base/utils/json.test
index 6e7854b744..bec4a665b6 100644
--- a/testing/btest/scripts/base/utils/json.test
+++ b/testing/btest/scripts/base/utils/json.test
@@ -122,4 +122,8 @@ event zeek_init()
 	print to_json(ta3);
 	print to_json(ta4);
 	print to_json(ta5, T);
+
+	# Opaque
+	local o1: opaque of topk = topk_init(5);
+	print to_json(o1);
 	}