diff --git a/src/mesa/tnl/t_context.c b/src/mesa/tnl/t_context.c
index e772a06..1d13bec 100644
--- a/src/mesa/tnl/t_context.c
+++ b/src/mesa/tnl/t_context.c
@@ -137,11 +137,19 @@ _tnl_InvalidateState( GLcontext *ctx, GLuint new_state )
       RENDERINPUTS_SET( tnl->render_inputs_bitset, _TNL_ATTRIB_COLOR_INDEX );
    }
 
-   if (ctx->Fog.Enabled ||
-       ((ctx->FragmentProgram._Active || ctx->FragmentProgram._Current) &&
-        (ctx->FragmentProgram._Current->FogOption != GL_NONE ||
-         (ctx->FragmentProgram._Current->Base.InputsRead & FRAG_BIT_FOGC))))
+   if (ctx->Fog.Enabled) {
+      /* fixed-function fog */
       RENDERINPUTS_SET( tnl->render_inputs_bitset, _TNL_ATTRIB_FOG );
+   }
+   else if (ctx->FragmentProgram._Active || ctx->FragmentProgram._Current) {
+      struct gl_fragment_program *fp = ctx->FragmentProgram._Current;
+      if (fp) {
+         if (fp->FogOption != GL_NONE || (fp->Base.InputsRead & FRAG_BIT_FOGC)) {
+            /* fragment program needs fog coord */
+            RENDERINPUTS_SET( tnl->render_inputs_bitset, _TNL_ATTRIB_FOG );
+         }
+      }
+   }
 
    if (ctx->Polygon.FrontMode != GL_FILL || 
        ctx->Polygon.BackMode != GL_FILL)