diff --git a/WoofWare.PawPrint.Domain/TypeConcretisation.fs b/WoofWare.PawPrint.Domain/TypeConcretisation.fs
index 757a666..5c83535 100644
--- a/WoofWare.PawPrint.Domain/TypeConcretisation.fs
+++ b/WoofWare.PawPrint.Domain/TypeConcretisation.fs
@@ -132,23 +132,6 @@ module ConcreteActivePatterns =
             | None -> None
         | _ -> None
 
-    let (|ConcreteBool|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
-        match handle with
-        | ConcreteTypeHandle.Concrete id ->
-            match concreteTypes.Mapping |> Map.tryFind id with
-            | Some ct ->
-                if
-                    ct.Assembly.Name = "System.Private.CoreLib"
-                    && ct.Namespace = "System"
-                    && ct.Name = "Boolean"
-                    && ct.Generics.IsEmpty
-                then
-                    Some ()
-                else
-                    None
-            | None -> None
-        | _ -> None
-
     let (|ConcreteChar|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
         match handle with
         | ConcreteTypeHandle.Concrete id ->
@@ -166,6 +149,23 @@ module ConcreteActivePatterns =
             | None -> None
         | _ -> None
 
+    let (|ConcreteBool|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
+        match handle with
+        | ConcreteTypeHandle.Concrete id ->
+            match concreteTypes.Mapping |> Map.tryFind id with
+            | Some ct ->
+                if
+                    ct.Assembly.Name = "System.Private.CoreLib"
+                    && ct.Namespace = "System"
+                    && ct.Name = "Boolean"
+                    && ct.Generics.IsEmpty
+                then
+                    Some ()
+                else
+                    None
+            | None -> None
+        | _ -> None
+
     let (|ConcreteString|_|) (concreteTypes : AllConcreteTypes) (handle : ConcreteTypeHandle) : unit option =
         match handle with
         | ConcreteTypeHandle.Concrete id ->
diff --git a/WoofWare.PawPrint/Intrinsics.fs b/WoofWare.PawPrint/Intrinsics.fs
index ce5a349..0d3438f 100644
--- a/WoofWare.PawPrint/Intrinsics.fs
+++ b/WoofWare.PawPrint/Intrinsics.fs
@@ -50,6 +50,11 @@ module Intrinsics =
         // https://github.com/dotnet/runtime/blob/108fa7856efcfd39bc991c2d849eabbf7ba5989c/src/coreclr/tools/Common/TypeSystem/IL/Stubs/UnsafeIntrinsics.cs#L192
         match methodToCall.DeclaringType.Assembly.Name, methodToCall.DeclaringType.Name, methodToCall.Name with
         | "System.Private.CoreLib", "Type", "get_TypeHandle" ->
+            // TODO: check return type is RuntimeTypeHandle
+            match methodToCall.Signature.ParameterTypes with
+            | _ :: _ -> failwith "bad signature Type.get_TypeHandle"
+            | _ -> ()
+
             // https://github.com/dotnet/runtime/blob/ec11903827fc28847d775ba17e0cd1ff56cfbc2e/src/libraries/System.Private.CoreLib/src/System/Type.cs#L470
 
             // TODO: check return type is RuntimeTypeHandle
@@ -379,5 +384,8 @@ module Intrinsics =
             |> IlMachineState.pushToEvalStack (CliType.Numeric (CliNumericType.Int32 size)) currentThread
             |> IlMachineState.advanceProgramCounter currentThread
             |> Some
+        | "System.Private.CoreLib", "RuntimeHelpers", "CreateSpan" ->
+            // https://github.com/dotnet/runtime/blob/9e5e6aa7bc36aeb2a154709a9d1192030c30a2ef/src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/RuntimeHelpers.cs#L153
+            None
         | a, b, c -> failwith $"TODO: implement JIT intrinsic {a}.{b}.{c}"
         |> Option.map (fun s -> s.WithThreadSwitchedToAssembly callerAssy currentThread |> fst)