diff --git a/WoofWare.Myriad.Plugins/TeqLicence.txt b/WoofWare.Myriad.Plugins/ApacheLicence.txt
similarity index 100%
rename from WoofWare.Myriad.Plugins/TeqLicence.txt
rename to WoofWare.Myriad.Plugins/ApacheLicence.txt
diff --git a/WoofWare.Myriad.Plugins/ArgParserGenerator.fs b/WoofWare.Myriad.Plugins/ArgParserGenerator.fs
index e7be6c5..6e13b6a 100644
--- a/WoofWare.Myriad.Plugins/ArgParserGenerator.fs
+++ b/WoofWare.Myriad.Plugins/ArgParserGenerator.fs
@@ -4,6 +4,7 @@ open System
 open System.Text
 open Fantomas.FCS.Syntax
 open Fantomas.FCS.Text.Range
+open TypeEquality
 open WoofWare.Whippet.Fantomas
 
 type internal ArgParserOutputSpec =
diff --git a/WoofWare.Myriad.Plugins/CataGenerator.fs b/WoofWare.Myriad.Plugins/CataGenerator.fs
index ef767b6..6b7d29c 100644
--- a/WoofWare.Myriad.Plugins/CataGenerator.fs
+++ b/WoofWare.Myriad.Plugins/CataGenerator.fs
@@ -1174,6 +1174,29 @@ module internal CataGenerator =
         ]
         |> SynModuleOrNamespace.createNamespace ns
 
+    /// This function comes from Myriad, and is therefore derived from an Apache 2.0-licenced work.
+    /// https://github.com/MoiraeSoftware/myriad/blob/3c9818faabf9d508c10c28d5ecd26e66fafb48a1/src/Myriad.Core/Ast.fs#L160
+    /// A copy of the Apache 2.0 licence is at ApacheLicence.txt.
+    let groupedTypeDefns (ast : ParsedInput) : (LongIdent * SynTypeDefn list) list =
+        let rec extractTypes (moduleDecls : SynModuleDecl list) (ns : LongIdent) =
+            [
+                for moduleDecl in moduleDecls do
+                    match moduleDecl with
+                    | SynModuleDecl.Types (types, _) -> yield (ns, types)
+                    | SynModuleDecl.NestedModule (SynComponentInfo (_, _, _, longId, _, _, _, _), _, decls, _, _, _) ->
+                        let combined = longId |> List.append ns
+                        yield! (extractTypes decls combined)
+                    | _ -> ()
+            ]
+
+        [
+            match ast with
+            | ParsedInput.ImplFile (ParsedImplFileInput (_, _, _, _, _, modules, _, _, _)) ->
+                for SynModuleOrNamespace (namespaceId, _, _, moduleDecls, _, _, _, _, _) in modules do
+                    yield! extractTypes moduleDecls namespaceId
+            | _ -> ()
+        ]
+
 open Myriad.Core
 
 /// Myriad generator that provides a catamorphism for an algebraic data type.
@@ -1187,7 +1210,7 @@ type CreateCatamorphismGenerator () =
             let ast, _ =
                 Ast.fromFilename context.InputFilename |> Async.RunSynchronously |> Array.head
 
-            let types = Ast.extractTypeDefn ast
+            let types = CataGenerator.groupedTypeDefns ast
 
             let opens = AstHelper.extractOpens ast
 
diff --git a/WoofWare.Myriad.Plugins/Teq.fs b/WoofWare.Myriad.Plugins/Teq.fs
deleted file mode 100644
index 860e345..0000000
--- a/WoofWare.Myriad.Plugins/Teq.fs
+++ /dev/null
@@ -1,18 +0,0 @@
-namespace WoofWare.Myriad.Plugins
-
-// Extracted from https://github.com/G-Research/TypeEquality
-// which is Apache-2.0 licenced. See `TeqLicence.txt`.
-// We inline this code because Myriad doesn't seem to reliably load package references in the generator.
-// I have reformatted a little, and stripped out all the code I don't use.
-
-type internal Teq<'a, 'b> = private | Teq of ('a -> 'b) * ('b -> 'a)
-
-[<RequireQualifiedAccess>]
-module internal Teq =
-
-    let refl<'a> : Teq<'a, 'a> = Teq (id, id)
-    let cast (Teq (f, _)) a = f a
-
-    [<RequireQualifiedAccess>]
-    module Cong =
-        let believeMe<'a, 'b, 'a2, 'b2> (_ : Teq<'a, 'b>) : Teq<'a2, 'b2> = unbox <| (refl : Teq<'a2, 'a2>)
diff --git a/WoofWare.Myriad.Plugins/WoofWare.Myriad.Plugins.fsproj b/WoofWare.Myriad.Plugins/WoofWare.Myriad.Plugins.fsproj
index 59df1bd..af29d92 100644
--- a/WoofWare.Myriad.Plugins/WoofWare.Myriad.Plugins.fsproj
+++ b/WoofWare.Myriad.Plugins/WoofWare.Myriad.Plugins.fsproj
@@ -20,6 +20,7 @@
 
   <ItemGroup>
     <PackageReference Include="Myriad.Core" Version="0.8.3" />
+    <PackageReference Include="TypeEquality" Version="0.3.0" />
     <PackageReference Include="WoofWare.Whippet.Fantomas" Version="0.2.1" />
     <!-- the lowest version allowed by Myriad.Core -->
     <PackageReference Update="FSharp.Core" Version="6.0.1" PrivateAssets="all"/>
@@ -28,7 +29,6 @@
   <ItemGroup>
     <Compile Include="List.fs"/>
     <Compile Include="Text.fs" />
-    <Compile Include="Teq.fs" />
     <Compile Include="Measure.fs" />
     <Compile Include="AstHelper.fs" />
     <Compile Include="RemoveOptionsGenerator.fs"/>
@@ -41,7 +41,7 @@
     <Compile Include="ArgParserGenerator.fs" />
     <Compile Include="Swagger.fs" />
     <Compile Include="SwaggerClientGenerator.fs" />
-    <None Include="TeqLicence.txt" />
+    <None Include="ApacheLicence.txt" />
     <EmbeddedResource Include="version.json"/>
     <EmbeddedResource Include="SurfaceBaseline.txt"/>
     <None Include="..\README.md">