diff --git a/doc/Doxyfile b/doc/Doxyfile
index 5ee5f82918..11593fba0e 100644
--- a/doc/Doxyfile
+++ b/doc/Doxyfile
@@ -778,7 +778,11 @@ INPUT                  = ../libs/ardour \
                          ../libs/widgets \
                          ../libs/zita-convolver \
                          ../libs/zita-resampler \
+                         ../libs/zita-resampler \
                          ../gtk2_ardour \
+                         ../libs/tk/ytkmm/ytkmm/gtkmm \
+                         ../libs/tk/ydkmm/ydkmm/gdkmm \
+                         ../libs/tk/ydk/ydk/gdk \
                          mainpage.txt
 
 ## audiographer assumes it's documented separately (has it's own @mainpage)
diff --git a/gtk2_ardour/ardour_ui.cc b/gtk2_ardour/ardour_ui.cc
index 95e71e8681..4c32ab8eb8 100644
--- a/gtk2_ardour/ardour_ui.cc
+++ b/gtk2_ardour/ardour_ui.cc
@@ -1499,6 +1499,10 @@ ARDOUR_UI::format_disk_space_label (float remain_sec)
 
 	std::string label = string_compose (X_("<span weight=\"ultralight\">%1</span>: "), _("Rec"));
 
+	if (_session && FLAC == _session->config.get_native_file_header_format () && remain_sec <= 86400) {
+		label += u8"\u2265"; // Greater-Than or Equal To
+	}
+
 	if (remain_sec > 86400) {
 		disk_space_label.set_markup (label + _(">24h"));
 	} else if (remain_sec > 32400 /* 9 hours */) {
diff --git a/gtk2_ardour/rec_info_box.cc b/gtk2_ardour/rec_info_box.cc
index 3d1cfd3951..ca51813429 100644
--- a/gtk2_ardour/rec_info_box.cc
+++ b/gtk2_ardour/rec_info_box.cc
@@ -340,20 +340,23 @@ RemainInfoBox::render (Cairo::RefPtr<Cairo::Context> const& cr, cairo_rectangle_
 		float remain_sec = samples / (float)sample_rate;
 		char buf[32];
 
+		bool  at_least     = FLAC == _session->config.get_native_file_header_format ();
+		const char* prefix = at_least ? u8"\u2265" : ""; // Greater-Than or Equal To
+
 		if (remain_sec > 86400) {
 			_layout_value->set_text (_(">24h"));
 		} else if (remain_sec > 32400 /* 9 hours */) {
-			snprintf (buf, sizeof (buf), "%.0f", remain_sec / 3600.f);
+			snprintf (buf, sizeof (buf), "%s%.0f", prefix, remain_sec / 3600.f);
 			_layout_value->set_text (std::string (buf) + S_("hours|h"));
 		} else if (remain_sec > 5940 /* 99 mins */) {
-			snprintf (buf, sizeof (buf), "%.1f", remain_sec / 3600.f);
+			snprintf (buf, sizeof (buf), "%s%.1f", prefix, remain_sec / 3600.f);
 			_layout_value->set_text (std::string (buf) + S_("hours|h"));
 		} else if (remain_sec > 60*3 /* 3 mins */) {
-			snprintf (buf, sizeof (buf), "%.0f", remain_sec / 60.f);
+			snprintf (buf, sizeof (buf), "%s%.0f", prefix, remain_sec / 60.f);
 			_layout_value->set_text (std::string (buf) + S_("minutes|m"));
 		} else {
 			Gtkmm2ext::set_source_rgb_a (cr, UIConfiguration::instance ().color ("alert:red"), .7);
-			snprintf (buf, sizeof (buf), "%.0f", remain_sec / 60.f);
+			snprintf (buf, sizeof (buf), "%s%.0f", prefix, remain_sec / 60.f);
 			_layout_value->set_text (std::string (buf) + S_("minutes|m"));
 		}
 	}
diff --git a/libs/ardour/ardour/session.h b/libs/ardour/ardour/session.h
index 2d26afce90..ebbb041bdc 100644
--- a/libs/ardour/ardour/session.h
+++ b/libs/ardour/ardour/session.h
@@ -2142,7 +2142,7 @@ private:
 
 	std::vector<space_and_path> session_dirs;
 	std::vector<space_and_path>::iterator last_rr_session_dir;
-	uint32_t _total_free_4k_blocks;
+	uint64_t _total_free_4k_blocks;
 	/** If this is true, _total_free_4k_blocks is not definite,
 	    as one or more of the session directories' filesystems
 	    could not report free space.