diff --git a/compiler/src/dmd/cppmangle.d b/compiler/src/dmd/cppmangle.d
index b015a642b9..2cee596138 100644
--- a/compiler/src/dmd/cppmangle.d
+++ b/compiler/src/dmd/cppmangle.d
@@ -213,6 +213,11 @@ private final class CppMangleVisitor : Visitor
     {
         auto tf = cast(TypeFunction)this.context.res.asFuncDecl().type;
         Type rt = preSemantic.nextOf();
+        // https://issues.dlang.org/show_bug.cgi?id=22739
+        // auto return type means that rt is null.
+        // if so, just pick up the type from the instance
+        if (!rt)
+            rt = tf.nextOf();
         if (tf.isref)
             rt = rt.referenceTo();
         auto prev = this.context.push(tf.nextOf());
diff --git a/compiler/test/compilable/test22739.d b/compiler/test/compilable/test22739.d
new file mode 100644
index 0000000000..6aeb5d60fd
--- /dev/null
+++ b/compiler/test/compilable/test22739.d
@@ -0,0 +1,10 @@
+// https://issues.dlang.org/show_bug.cgi?id=22739
+
+extern(C++) auto f(T)()
+{
+    return T.init;
+}
+void main()
+{
+    f!int;
+}