latency tracer: element-latency not working when capsfilter is in the pipeline

For some reason the element-latency isn't working if I have a capsfilter in my pipeline.

This is working:

$ GST_DEBUG="GST_TRACER:7" GST_TRACERS="latency(flags=pipeline+element+reported)" GST_DEBUG_FILE=gst.log gst-launch-1.0 videotestsrc num-buffers=100 ! x264enc ! fakesink silent=false -v

(...)

$ grep element-latency gst.log  | grep x264enc | wc -l
26

But this is not:

$ GST_DEBUG="GST_TRACER:7" GST_TRACERS="latency(flags=pipeline+element+reported)" GST_DEBUG_FILE=gst.log gst-launch-1.0 videotestsrc num-buffers=100 ! video/x-raw,format=NV12,width=320,height=240 ! x264enc ! fakesink silent=false -v

(...)

$ grep element-latency gst.log  | grep x264enc | wc -l
0

In both cases buffers are reaching fakesink so the encoder does produce buffers.