diff --git a/screen-write.c b/screen-write.c
index e6cc0d59..97a11998 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -1131,7 +1131,7 @@ screen_write_insertcharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
 	grid_view_insert_cells(s->grid, s->cx, s->cy, nx, bg);
 
 	screen_write_collect_flush(ctx, 0, __func__);
-	ttyctx.num = nx;
+	ttyctx.n = nx;
 	tty_write(tty_cmd_insertcharacter, &ttyctx);
 }
 
@@ -1164,7 +1164,7 @@ screen_write_deletecharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
 	grid_view_delete_cells(s->grid, s->cx, s->cy, nx, bg);
 
 	screen_write_collect_flush(ctx, 0, __func__);
-	ttyctx.num = nx;
+	ttyctx.n = nx;
 	tty_write(tty_cmd_deletecharacter, &ttyctx);
 }
 
@@ -1197,7 +1197,7 @@ screen_write_clearcharacter(struct screen_write_ctx *ctx, u_int nx, u_int bg)
 	grid_view_clear(s->grid, s->cx, s->cy, nx, 1, bg);
 
 	screen_write_collect_flush(ctx, 0, __func__);
-	ttyctx.num = nx;
+	ttyctx.n = nx;
 	tty_write(tty_cmd_clearcharacter, &ttyctx);
 }
 
@@ -1233,7 +1233,7 @@ screen_write_insertline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
 		grid_view_insert_lines(gd, s->cy, ny, bg);
 
 		screen_write_collect_flush(ctx, 0, __func__);
-		ttyctx.num = ny;
+		ttyctx.n = ny;
 		tty_write(tty_cmd_insertline, &ttyctx);
 		return;
 	}
@@ -1253,7 +1253,7 @@ screen_write_insertline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
 
 	screen_write_collect_flush(ctx, 0, __func__);
 
-	ttyctx.num = ny;
+	ttyctx.n = ny;
 	tty_write(tty_cmd_insertline, &ttyctx);
 }
 
@@ -1286,7 +1286,7 @@ screen_write_deleteline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
 		grid_view_delete_lines(gd, s->cy, ny, bg);
 
 		screen_write_collect_flush(ctx, 0, __func__);
-		ttyctx.num = ny;
+		ttyctx.n = ny;
 		tty_write(tty_cmd_deleteline, &ttyctx);
 		return;
 	}
@@ -1305,7 +1305,7 @@ screen_write_deleteline(struct screen_write_ctx *ctx, u_int ny, u_int bg)
 		grid_view_delete_lines_region(gd, s->rlower, s->cy, ny, bg);
 
 	screen_write_collect_flush(ctx, 0, __func__);
-	ttyctx.num = ny;
+	ttyctx.n = ny;
 	tty_write(tty_cmd_deleteline, &ttyctx);
 }
 
@@ -1567,7 +1567,7 @@ screen_write_scrolldown(struct screen_write_ctx *ctx, u_int lines, u_int bg)
 		grid_view_scroll_region_down(gd, s->rupper, s->rlower, bg);
 
 	screen_write_collect_flush(ctx, 0, __func__);
-	ttyctx.num = lines;
+	ttyctx.n = lines;
 	tty_write(tty_cmd_scrolldown, &ttyctx);
 }
 
@@ -1847,7 +1847,7 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 			ctx->scrolled = s->rlower - s->rupper + 1;
 
 		screen_write_initctx(ctx, &ttyctx, 1);
-		ttyctx.num = ctx->scrolled;
+		ttyctx.n = ctx->scrolled;
 		ttyctx.bg = ctx->bg;
 		tty_write(tty_cmd_scrollup, &ttyctx);
 
@@ -1875,15 +1875,15 @@ screen_write_collect_flush(struct screen_write_ctx *ctx, int scroll_only,
 			if (ci->type == CLEAR) {
 				screen_write_initctx(ctx, &ttyctx, 1);
 				ttyctx.bg = ci->bg;
-				ttyctx.num = ci->used;
+				ttyctx.n = ci->used;
 				tty_write(tty_cmd_clearcharacter, &ttyctx);
 			} else {
 				screen_write_initctx(ctx, &ttyctx, 0);
 				ttyctx.cell = &ci->gc;
 				if (ci->wrapped)
 					ttyctx.flags |= TTY_CTX_WRAPPED;
-				ttyctx.ptr = cl->data + ci->x;
-				ttyctx.num = ci->used;
+				ttyctx.data.data = cl->data + ci->x;
+				ttyctx.data.size = ci->used;
 				tty_write(tty_cmd_cells, &ttyctx);
 			}
 			items++;
@@ -2176,7 +2176,7 @@ screen_write_cell(struct screen_write_ctx *ctx, const struct grid_cell *gc)
 	/* Create space for character in insert mode. */
 	if (s->mode & MODE_INSERT) {
 		screen_write_collect_flush(ctx, 0, __func__);
-		ttyctx.num = width;
+		ttyctx.n = width;
 		tty_write(tty_cmd_insertcharacter, &ttyctx);
 	}
 
@@ -2388,9 +2388,9 @@ screen_write_setselection(struct screen_write_ctx *ctx, const char *clip,
 	struct tty_ctx	ttyctx;
 
 	screen_write_initctx(ctx, &ttyctx, 0);
-	ttyctx.ptr = str;
-	ttyctx.ptr2 = (void *)clip;
-	ttyctx.num = len;
+	ttyctx.sel.clip = clip;
+	ttyctx.sel.data = str;
+	ttyctx.sel.size = len;
 
 	tty_write(tty_cmd_setselection, &ttyctx);
 }
@@ -2405,8 +2405,8 @@ screen_write_rawstring(struct screen_write_ctx *ctx, u_char *str, u_int len,
 	screen_write_initctx(ctx, &ttyctx, 0);
 	if (allow_invisible_panes)
 		ttyctx.flags |= TTY_CTX_INVISIBLE_PANES;
-	ttyctx.ptr = str;
-	ttyctx.num = len;
+	ttyctx.data.data = str;
+	ttyctx.data.size = len;
 
 	tty_write(tty_cmd_rawstring, &ttyctx);
 }
diff --git a/tmux.h b/tmux.h
index 47228afb..50092e90 100644
--- a/tmux.h
+++ b/tmux.h
@@ -1741,9 +1741,20 @@ struct tty_ctx {
 #define TTY_CTX_CELL_DRAW_LINE 0x20
 #define TTY_CTX_CELL_INVALIDATE 0x40
 
-	u_int		 num;
-	void		*ptr;
-	void		*ptr2;
+	union {
+		u_int			 n;
+
+		struct {
+			const char	*data;
+			size_t		 size;
+		} data;
+
+		struct {
+			const char	*clip;
+			const char	*data;
+			size_t		 size;
+		} sel;
+	};
 
 	/*
 	 * Cursor and region position before the screen was updated - this is
diff --git a/tty.c b/tty.c
index fd22df11..a11c5af3 100644
--- a/tty.c
+++ b/tty.c
@@ -1625,7 +1625,7 @@ tty_cmd_insertcharacter(struct tty *tty, const struct tty_ctx *ctx)
 
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
-	tty_emulate_repeat(tty, TTYC_ICH, TTYC_ICH1, ctx->num);
+	tty_emulate_repeat(tty, TTYC_ICH, TTYC_ICH1, ctx->n);
 }
 
 void
@@ -1648,7 +1648,7 @@ tty_cmd_deletecharacter(struct tty *tty, const struct tty_ctx *ctx)
 
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
-	tty_emulate_repeat(tty, TTYC_DCH, TTYC_DCH1, ctx->num);
+	tty_emulate_repeat(tty, TTYC_DCH, TTYC_DCH1, ctx->n);
 }
 
 void
@@ -1657,7 +1657,7 @@ tty_cmd_clearcharacter(struct tty *tty, const struct tty_ctx *ctx)
 	tty_default_attributes(tty, &ctx->defaults, ctx->palette, ctx->bg,
 	    ctx->s->hyperlinks);
 
-	tty_clear_pane_line(tty, ctx, ctx->ocy, ctx->ocx, ctx->num, ctx->bg);
+	tty_clear_pane_line(tty, ctx, ctx->ocy, ctx->ocx, ctx->n, ctx->bg);
 }
 
 void
@@ -1684,7 +1684,7 @@ tty_cmd_insertline(struct tty *tty, const struct tty_ctx *ctx)
 	tty_margin_off(tty);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
-	tty_emulate_repeat(tty, TTYC_IL, TTYC_IL1, ctx->num);
+	tty_emulate_repeat(tty, TTYC_IL, TTYC_IL1, ctx->n);
 	tty->cx = tty->cy = UINT_MAX;
 }
 
@@ -1712,7 +1712,7 @@ tty_cmd_deleteline(struct tty *tty, const struct tty_ctx *ctx)
 	tty_margin_off(tty);
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->ocy);
 
-	tty_emulate_repeat(tty, TTYC_DL, TTYC_DL1, ctx->num);
+	tty_emulate_repeat(tty, TTYC_DL, TTYC_DL1, ctx->n);
 	tty->cx = tty->cy = UINT_MAX;
 }
 
@@ -1845,19 +1845,19 @@ tty_cmd_scrollup(struct tty *tty, const struct tty_ctx *ctx)
 	tty_region_pane(tty, ctx, ctx->orupper, ctx->orlower);
 	tty_margin_pane(tty, ctx);
 
-	if (ctx->num == 1 || !tty_term_has(tty->term, TTYC_INDN)) {
+	if (ctx->n == 1 || !tty_term_has(tty->term, TTYC_INDN)) {
 		if (!tty_use_margin(tty))
 			tty_cursor(tty, 0, tty->rlower);
 		else
 			tty_cursor(tty, tty->rright, tty->rlower);
-		for (i = 0; i < ctx->num; i++)
+		for (i = 0; i < ctx->n; i++)
 			tty_putc(tty, '\n');
 	} else {
 		if (tty->cy == UINT_MAX)
 			tty_cursor(tty, 0, 0);
 		else
 			tty_cursor(tty, 0, tty->cy);
-		tty_putcode_i(tty, TTYC_INDN, ctx->num);
+		tty_putcode_i(tty, TTYC_INDN, ctx->n);
 	}
 }
 
@@ -1888,9 +1888,9 @@ tty_cmd_scrolldown(struct tty *tty, const struct tty_ctx *ctx)
 	tty_cursor_pane(tty, ctx, ctx->ocx, ctx->orupper);
 
 	if (tty_term_has(tty->term, TTYC_RIN))
-		tty_putcode_i(tty, TTYC_RIN, ctx->num);
+		tty_putcode_i(tty, TTYC_RIN, ctx->n);
 	else {
-		for (i = 0; i < ctx->num; i++)
+		for (i = 0; i < ctx->n; i++)
 			tty_putcode(tty, TTYC_RI);
 	}
 }
@@ -2040,14 +2040,15 @@ tty_cmd_cells(struct tty *tty, const struct tty_ctx *ctx)
 	struct visible_ranges	*r;
 	struct visible_range	*rr;
 	u_int			 i, px, py, cx;
-	char			*cp = ctx->ptr;
+	const char		*cp = ctx->data.data;
+	size_t			 n = ctx->data.size;
 
-	if (!tty_is_visible(tty, ctx, ctx->ocx, ctx->ocy, ctx->num, 1))
+	if (!tty_is_visible(tty, ctx, ctx->ocx, ctx->ocy, n, 1))
 		return;
 
 	if ((ctx->flags & TTY_CTX_WINDOW_BIGGER) &&
 	    (ctx->xoff + ctx->ocx < ctx->wox ||
-	    ctx->xoff + ctx->ocx + ctx->num > ctx->wox + ctx->wsx)) {
+	    ctx->xoff + ctx->ocx + n > ctx->wox + ctx->wsx)) {
 		if ((~ctx->flags & TTY_CTX_WRAPPED) ||
 		    !tty_full_width(tty, ctx) ||
 		    (tty->term->flags & TERM_NOAM) ||
@@ -2070,7 +2071,7 @@ tty_cmd_cells(struct tty *tty, const struct tty_ctx *ctx)
 	px = ctx->xoff + ctx->ocx - ctx->wox;
 	py = ctx->yoff + ctx->ocy - ctx->woy;
 
-	r = tty_check_overlay_range(tty, px, py, ctx->num);
+	r = tty_check_overlay_range(tty, px, py, n);
 	for (i = 0; i < r->used; i++) {
 		rr = &r->ranges[i];
 		if (rr->nx != 0) {
@@ -2084,7 +2085,7 @@ tty_cmd_cells(struct tty *tty, const struct tty_ctx *ctx)
 void
 tty_cmd_setselection(struct tty *tty, const struct tty_ctx *ctx)
 {
-	tty_set_selection(tty, ctx->ptr2, ctx->ptr, ctx->num);
+	tty_set_selection(tty, ctx->sel.clip, ctx->sel.data, ctx->sel.size);
 }
 
 void
@@ -2113,7 +2114,7 @@ void
 tty_cmd_rawstring(struct tty *tty, const struct tty_ctx *ctx)
 {
 	tty->flags |= TTY_NOBLOCK;
-	tty_add(tty, ctx->ptr, ctx->num);
+	tty_add(tty, ctx->data.data, ctx->data.size);
 	tty_invalidate(tty);
 }