Shader: Correct directional lightmap decoding in custom lighting function

I'm trying to get custom lighting as seen in these examples to work with my shaders. I can't, however, seem to get beyond rudimentary lightmap functionality to work - directional lightmaps should give bump/spec on my lightmapped objects, right?

Bump doesn't show for me with the shader below. It's copied almost verbatim from the examples, I only added a bumpmap slot.

If line 10 is changed to "Lambert" rather than "Standard", it works.

Any ideas?

 Shader "Test/ShaderTestLM1" {
     Properties {
         _MainTex ("Texture", 2D) = "white" {}
         _BumpMap ("Bumpmap 1", 2D) = "bump" {}
     }
 SubShader {
     Tags { "RenderType" = "Opaque" }
         CGPROGRAM
 
         #pragma surface surf Standard
 
         half4 LightingStandard (SurfaceOutput s, half3 lightDir, half atten) {
             half NdotL = dot (s.Normal, lightDir);
             half4 c; c.rgb = s.Albedo * _LightColor0.rgb * (NdotL * atten * 2);
             c.a = s.Alpha;
             return c;
         }
 
         inline fixed4 LightingStandard_SingleLightmap (SurfaceOutput s, fixed4 color) {
             half3 lm = DecodeLightmap (color);
             return fixed4(lm, 0);
         }
 
         inline fixed4 LightingStandard_DualLightmap (SurfaceOutput s, fixed4 totalColor, fixed4 indirectOnlyColor, half indirectFade) {
             half3 lm = lerp (DecodeLightmap (indirectOnlyColor), DecodeLightmap (totalColor), indirectFade);
             return fixed4(lm, 0);
         }
 
         inline fixed4 LightingStandard_StandardLightmap (SurfaceOutput s, fixed4 color, fixed4 scale, bool surfFuncWritesNormal) {
             UNITY_DIRBASIS
 
             half3 lm = DecodeLightmap (color);
             half3 scalePerBasisVector = DecodeLightmap (scale);
 
             if (surfFuncWritesNormal)
             {
                 half3 normalInRnmBasis = saturate (mul (unity_DirBasis, s.Normal));
                 lm *= dot (normalInRnmBasis, scalePerBasisVector);
                 
             }
             return fixed4(lm, 0);
         }
 
         struct Input {
             float2 uv_MainTex;
             float2 uv_BumpMap;
         };
 
         sampler2D _MainTex;
         sampler2D _BumpMap;
 
         void surf (Input IN, inout SurfaceOutput o) {
         
             o.Albedo = tex2D (_MainTex, IN.uv_MainTex).rgb;
             o.Normal = UnpackNormal ( tex2D( _BumpMap, IN.uv_BumpMap ) );
         
         }
         ENDCG
     }
     Fallback "Additive"
 }