diff --git a/eeshow/gui/common.h b/eeshow/gui/common.h
index 0d35814..bfe2f3e 100644
--- a/eeshow/gui/common.h
+++ b/eeshow/gui/common.h
@@ -72,6 +72,7 @@ struct gui_ctx {
 	bool showing_history;
 	enum selecting {
 		sel_only,	/* select the only revision we show */
+		sel_split,	/* select revision to compare with */
 		sel_new,	/* select the new revision */
 		sel_old,	/* select the old revision */
 	} selecting;
diff --git a/eeshow/gui/history.c b/eeshow/gui/history.c
index 3c62975..8a2b117 100644
--- a/eeshow/gui/history.c
+++ b/eeshow/gui/history.c
@@ -49,6 +49,7 @@ static void set_history_style(struct gui_hist *h, bool current)
 
 	switch (ctx->selecting) {
 	case sel_only:
+	case sel_split:
 		style.frame = COLOR(FRAME_SEL_ONLY);
 		break;
 	case sel_old:
@@ -120,6 +121,9 @@ static void click_history(void *user)
 
 	switch (ctx->selecting) {
 	case sel_only:
+		ctx->new_hist = h;
+		break;
+	case sel_split:
 		ctx->old_hist = ctx->new_hist;
 		ctx->new_hist = h;
 		break;
@@ -135,19 +139,21 @@ static void click_history(void *user)
 
 	ctx->diff_mode = diff_delta;
 
-	if (ctx->new_hist->age > ctx->old_hist->age) {
-		swap(ctx->new_hist, ctx->old_hist);
-		if (ctx->selecting == sel_old) {
-			go_to_sheet(ctx, sheet);
+	if (ctx->old_hist) {
+		if (ctx->new_hist->age > ctx->old_hist->age) {
+			swap(ctx->new_hist, ctx->old_hist);
+			if (ctx->selecting == sel_old) {
+				go_to_sheet(ctx, sheet);
+			} else {
+				go_to_sheet(ctx, old_sheet);
+				render_delta(ctx);
+			}
 		} else {
-			go_to_sheet(ctx, old_sheet);
-			render_delta(ctx);
+			if (ctx->selecting != sel_old)
+				go_to_sheet(ctx, sheet);
+			else
+				render_delta(ctx);
 		}
-	} else {
-		if (ctx->selecting != sel_old)
-			go_to_sheet(ctx, sheet);
-		else
-			render_delta(ctx);
 	}
 
 	if (ctx->old_hist == ctx->new_hist)
diff --git a/eeshow/gui/sheet.c b/eeshow/gui/sheet.c
index 111756b..1baf3ac 100644
--- a/eeshow/gui/sheet.c
+++ b/eeshow/gui/sheet.c
@@ -173,8 +173,11 @@ static void show_diff_cb(void *user)
 {
 	struct gui_ctx *ctx = user;
 
-	set_diff_mode(ctx,
-	    ctx->diff_mode == diff_delta ? diff_new : diff_delta);
+	if (ctx->old_hist)
+		set_diff_mode(ctx,
+		    ctx->diff_mode == diff_delta ? diff_new : diff_delta);
+	else
+		show_history(ctx, sel_split);
 }
 
 
@@ -184,11 +187,25 @@ static void toggle_old_new(struct gui_ctx *ctx)
 }
 
 
+static void add_delta(struct gui_ctx *ctx)
+{
+	struct overlay *over;
+	struct overlay_style style;
+
+	over = overlay_add(&ctx->hist_overlays, &ctx->aois,
+	    NULL, show_diff_cb, ctx);
+	style = overlay_style_default;
+	if (ctx->old_hist && ctx->diff_mode == diff_delta)
+		style.frame = RGBA(0, 0, 0, 1);
+	overlay_style(over, &style);
+	overlay_text(over, "Δ");
+}
+
+
 static void revision_overlays_diff(struct gui_ctx *ctx)
 {
 	struct gui_hist *new = ctx->new_hist;
 	struct gui_hist *old = ctx->old_hist;
-	struct overlay *over;
 	struct overlay_style style;
 
 	new->over = overlay_add(&ctx->hist_overlays, &ctx->aois,
@@ -199,13 +216,7 @@ static void revision_overlays_diff(struct gui_ctx *ctx)
 	overlay_style(new->over, &style);
 	show_history_details(new, 0);
 
-	over = overlay_add(&ctx->hist_overlays, &ctx->aois,
-	    NULL, show_diff_cb, ctx);
-	style = overlay_style_default;
-	if (ctx->diff_mode == diff_delta)
-		style.frame = RGBA(0, 0, 0, 1);
-	overlay_style(over, &style);
-	overlay_text(over, "Δ");
+	add_delta(ctx);
 
 	old->over = overlay_add(&ctx->hist_overlays, &ctx->aois,
 	    show_history_details, show_history_cb, old);
@@ -229,6 +240,8 @@ void do_revision_overlays(struct gui_ctx *ctx)
 		    ctx->new_hist);
 		overlay_style(ctx->new_hist->over, &overlay_style_default);
 		show_history_details(ctx->new_hist, 0);
+
+		add_delta(ctx);
 	}
 }