g-i: Warning: GstValidate: symbol='...': Skipping foreign symbol from namespace GstPbutils

Strange warnings when building GstValidate-1.0.gir (leading paths removed for readability):

[621/838] Generating GstValidate-1.0.gir with a custom command.
gst-validate-bin-monitor.h:34: Warning: GstValidate: symbol='GST_IS_VALIDATE_BIN_MONITOR': Skipping foreign symbol from namespace GstPbutils
gst-validate-bin-monitor.h:35: Warning: GstValidate: symbol='GST_IS_VALIDATE_BIN_MONITOR_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-pipeline-monitor.h:33: Warning: GstValidate: symbol='GST_IS_VALIDATE_PIPELINE_MONITOR': Skipping foreign symbol from namespace GstPbutils
gst-validate-pipeline-monitor.h:34: Warning: GstValidate: symbol='GST_IS_VALIDATE_PIPELINE_MONITOR_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-element-monitor.h:33: Warning: GstValidate: symbol='GST_IS_VALIDATE_ELEMENT_MONITOR': Skipping foreign symbol from namespace GstPbutils
gst-validate-element-monitor.h:34: Warning: GstValidate: symbol='GST_IS_VALIDATE_ELEMENT_MONITOR_CLASS': Skipping foreign symbol from namespace GstPbutils
media-descriptor.h:143: Warning: GstValidate: symbol='GST_IS_VALIDATE_MEDIA_DESCRIPTOR': Skipping foreign symbol from namespace GstPbutils
media-descriptor.h:144: Warning: GstValidate: symbol='GST_IS_VALIDATE_MEDIA_DESCRIPTOR_CLASS': Skipping foreign symbol from namespace GstPbutils
media-descriptor-writer.h:39: Warning: GstValidate: symbol='GST_IS_VALIDATE_MEDIA_DESCRIPTOR_WRITER': Skipping foreign symbol from namespace GstPbutils
media-descriptor-writer.h:40: Warning: GstValidate: symbol='GST_IS_VALIDATE_MEDIA_DESCRIPTOR_WRITER_CLASS': Skipping foreign symbol from namespace GstPbutils
media-descriptor-parser.h:38: Warning: GstValidate: symbol='GST_IS_VALIDATE_MEDIA_DESCRIPTOR_PARSER': Skipping foreign symbol from namespace GstPbutils
media-descriptor-parser.h:39: Warning: GstValidate: symbol='GST_IS_VALIDATE_MEDIA_DESCRIPTOR_PARSER_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-monitor.h:40: Warning: GstValidate: symbol='GST_IS_VALIDATE_MONITOR': Skipping foreign symbol from namespace GstPbutils
gst-validate-monitor.h:41: Warning: GstValidate: symbol='GST_IS_VALIDATE_MONITOR_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-override.h:85: Warning: GstValidate: symbol='GST_IS_VALIDATE_OVERRIDE': Skipping foreign symbol from namespace GstPbutils
gst-validate-override.h:86: Warning: GstValidate: symbol='GST_IS_VALIDATE_OVERRIDE_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-pad-monitor.h:38: Warning: GstValidate: symbol='GST_IS_VALIDATE_PAD_MONITOR': Skipping foreign symbol from namespace GstPbutils
gst-validate-pad-monitor.h:39: Warning: GstValidate: symbol='GST_IS_VALIDATE_PAD_MONITOR_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-reporter.h:37: Warning: GstValidate: symbol='GST_IS_VALIDATE_REPORTER': Skipping foreign symbol from namespace GstPbutils
gst-validate-runner.h:39: Warning: GstValidate: symbol='GST_IS_VALIDATE_RUNNER': Skipping foreign symbol from namespace GstPbutils
gst-validate-runner.h:40: Warning: GstValidate: symbol='GST_IS_VALIDATE_RUNNER_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-scenario.h:36: Warning: GstValidate: symbol='GST_IS_VALIDATE_SCENARIO': Skipping foreign symbol from namespace GstPbutils
gst-validate-scenario.h:37: Warning: GstValidate: symbol='GST_IS_VALIDATE_SCENARIO_CLASS': Skipping foreign symbol from namespace GstPbutils
gst-validate-scenario.h:142: Warning: GstValidate: symbol='GST_IS_VALIDATE_ACTION': Skipping foreign symbol from namespace GstPbutils
gst-validate-scenario.h:215: Warning: GstValidate: symbol='GST_IS_VALIDATE_ACTION_TYPE': Skipping foreign symbol from namespace GstPbutils