imcomplete type??

Given struct defs of:

struct gen_state {
        struct localuser *u;
        struct ast_filestream *stream;
               **************
        int sample_queue;
        int playing_silence;
};


struct ast_filestream {
        /* Everybody reserves a block of AST_RESERVED_POINTERS pointers for us */
        struct ast_format *fmt;
        int flags;
        mode_t mode;
        char *filename;
             **********
        char *realfilename;
        /* Video file stream */
        struct ast_filestream *vfs;
        /* Transparently translate from another format -- just once */
        struct ast_trans_pvt *trans;
        struct ast_tranlator_pvt *tr;
        int lastwriteformat;
        int lasttimeout;
        struct ast_channel *owner;
};

and

struct gen_state *state;

Why does this:

fprintf(child_events, "F,%10ld,%s\n", time(NULL),state->stream->filename);

produce this error:

app.c:166: error: dereferencing pointer to incomplete type

?????


Thanks for your help.