diff --git a/bin/dart_fidl_json/json.fidlmerge b/bin/dart_fidl_json/json.fidlmerge
index f1c0b7c..495a575 100644
--- a/bin/dart_fidl_json/json.fidlmerge
+++ b/bin/dart_fidl_json/json.fidlmerge
@@ -330,7 +330,7 @@
   {{- template "FileHeader" . }}
   {{- template "FidlInclude" . }}
   {{- template "EnumConverterDecls" . }}
-  {{- template "UnionConverterDecls" .XUnions }}
+  {{- template "UnionConverterDecls" .Unions }}
   {{- template "StructConverterDecls" . }}
   {{- template "TableConverterDecls" . }}
 {{- end }}
diff --git a/bin/fidlgen_dart/backend/ir/ir.go b/bin/fidlgen_dart/backend/ir/ir.go
index 0de8658..3798432 100644
--- a/bin/fidlgen_dart/backend/ir/ir.go
+++ b/bin/fidlgen_dart/backend/ir/ir.go
@@ -1169,10 +1169,6 @@
 		root.Unions = append(root.Unions, c.compileUnion(v))
 	}
 
-	if len(r.XUnions) > 0 {
-		panic("xunions should not be used anymore")
-	}
-
 	for _, v := range r.Interfaces {
 		root.Interfaces = append(root.Interfaces, c.compileInterface(v))
 	}