diff --git a/src/Glutinum.Converter/Transform.fs b/src/Glutinum.Converter/Transform.fs
index 72796b3..ea80926 100644
--- a/src/Glutinum.Converter/Transform.fs
+++ b/src/Glutinum.Converter/Transform.fs
@@ -200,6 +200,9 @@ let rec private transformType
 
         if isOptional && others.Length = 1 then
             FSharpType.Option(transformType context others.Head)
+        // Don't wrap in a U1 if there is only one case
+        else if others.Length = 1 then
+            transformType context others.Head
         else
             {
                 Attributes = []
diff --git a/tests/specs/references/unionType/singleUnionResolved.d.ts b/tests/specs/references/unionType/singleUnionResolved.d.ts
new file mode 100644
index 0000000..3fb116e
--- /dev/null
+++ b/tests/specs/references/unionType/singleUnionResolved.d.ts
@@ -0,0 +1 @@
+export type ColorInfo = number | false;
diff --git a/tests/specs/references/unionType/singleUnionResolved.fsx b/tests/specs/references/unionType/singleUnionResolved.fsx
new file mode 100644
index 0000000..fd50d1e
--- /dev/null
+++ b/tests/specs/references/unionType/singleUnionResolved.fsx
@@ -0,0 +1,12 @@
+module rec Glutinum
+
+open Fable.Core
+open Fable.Core.JsInterop
+open System
+
+type ColorInfo =
+    float
+
+(***)
+#r "nuget: Fable.Core"
+(***)