Standard Surface Shader ambient occlusion uv2 doesn't work in forward rendering

Hi,

I added occlusion to the standard shader using uv2 and it works perfectly in deferred mode. If I use forward rendering, occlusion is completely missing. I used the Create/Shader/Standard Surface Shader dropdown and added a very simple small modification.

Code (csharp):

1.  
2. Shader "Custom/StandardUV2Occlusion" {
3.    Properties {
4.      _Color ("Color", Color) = (1,1,1,1)
5.      _MainTex ("Albedo (RGB)", 2D) = "white" {}
6.      _OcclusionMap("Occlusion", 2D) = "white" {} // Occlusion texture
7.      _Glossiness ("Smoothness", Range(0,1)) = 0.5
8.      _Metallic ("Metallic", Range(0,1)) = 0.0
9.      _OcclusionStrength("Occlusion intensity", Range(0,1)) = 1.0 // Occlusion intensity
10.    }
11.    SubShader {
12.      Tags { "RenderType"="Opaque" }
13.      LOD 200
14.      
15.      CGPROGRAM
16.      // Physically based Standard lighting model, and enable shadows on all light types
17.      #pragma surface surf Standard fullforwardshadows
18.  
19.      // Use shader model 3.0 target, to get nicer looking lighting
20.      #pragma target 3.0
21.  
22.      sampler2D _MainTex, _OcclusionMap;
23.  
24.      struct Input {
25.        float2 uv_MainTex;
26.        float2 uv2_OcclusionMap; // use the second uv set
27.      };
28.  
29.      half _Glossiness;
30.      half _Metallic;
31.      half _OcclusionStrength;
32.      fixed4 _Color;
33.  
34.      void surf (Input IN, inout SurfaceOutputStandard o) {
35.        // Albedo comes from a texture tinted by color
36.        fixed4 c = tex2D (_MainTex, IN.uv_MainTex) * _Color;
37.        o.Albedo = c.rgb;
38.        // Metallic and smoothness come from slider variables
39.        o.Metallic = _Metallic;
40.        o.Smoothness = _Glossiness;
41.        o.Alpha = c.a;
42.        o.Occlusion = lerp(1.0, tex2D(_OcclusionMap, IN.uv2_OcclusionMap), _OcclusionStrength);
43. // interpolate the multiplication of occlusion via OcclusionStrength
44.      }
45.      ENDCG
46.    }
47.    FallBack "Diffuse"
48. }
49.  

The manual has no mention of uv2 only working in deferred, so I assume I made a mistake somewhere. If anyone can help me I would be very grateful.