diff --git a/fftools/ffmpeg.h b/fftools/ffmpeg.h
index 6750432a81..fa726575f4 100644
--- a/fftools/ffmpeg.h
+++ b/fftools/ffmpeg.h
@@ -656,7 +656,6 @@ enum AVPixelFormat choose_pixel_fmt(AVStream *st, AVCodecContext *avctx,
 int configure_filtergraph(FilterGraph *fg);
 int configure_output_filter(FilterGraph *fg, OutputFilter *ofilter, AVFilterInOut *out);
 void check_filter_outputs(void);
-int ist_in_filtergraph(FilterGraph *fg, InputStream *ist);
 int filtergraph_is_simple(FilterGraph *fg);
 int init_simple_filtergraph(InputStream *ist, OutputStream *ost);
 int init_complex_filtergraph(FilterGraph *fg);
diff --git a/fftools/ffmpeg_filter.c b/fftools/ffmpeg_filter.c
index c2b7ece95d..00534d7e92 100644
--- a/fftools/ffmpeg_filter.c
+++ b/fftools/ffmpeg_filter.c
@@ -1176,15 +1176,6 @@ int ifilter_parameters_from_frame(InputFilter *ifilter, const AVFrame *frame)
     return 0;
 }
 
-int ist_in_filtergraph(FilterGraph *fg, InputStream *ist)
-{
-    int i;
-    for (i = 0; i < fg->nb_inputs; i++)
-        if (fg->inputs[i]->ist == ist)
-            return 1;
-    return 0;
-}
-
 int filtergraph_is_simple(FilterGraph *fg)
 {
     return !fg->graph_desc;