diff --git a/grid.c b/grid.c
index 6ca14cba..7943d3be 100644
--- a/grid.c
+++ b/grid.c
@@ -76,7 +76,7 @@ grid_need_extended_cell(const struct grid_cell_entry *gce,
 		return (1);
 	if (gc->attr > 0xff)
 		return (1);
-	if (gc->data.size > 1 || gc->data.width > 1)
+	if (gc->data.size != 1 || gc->data.width != 1)
 		return (1);
 	if ((gc->fg & COLOUR_FLAG_RGB) || (gc->bg & COLOUR_FLAG_RGB))
 		return (1);
@@ -570,7 +570,7 @@ grid_set_cells(struct grid *gd, u_int px, u_int py, const struct grid_cell *gc,
 		gce = &gl->celldata[px + i];
 		if (grid_need_extended_cell(gce, gc)) {
 			gee = grid_extended_cell(gl, gce, gc);
-			gee->data = utf8_build_one(s[i], 1);
+			gee->data = utf8_build_one(s[i]);
 		} else
 			grid_store_cell(gce, gc, s[i]);
 	}
diff --git a/screen-write.c b/screen-write.c
index 33e3f975..68c3aa76 100644
--- a/screen-write.c
+++ b/screen-write.c
@@ -39,7 +39,7 @@ static const struct grid_cell *screen_write_combine(struct screen_write_ctx *,
 		    const struct utf8_data *, u_int *);
 
 static const struct grid_cell screen_write_pad_cell = {
-	{ { ' ' }, 0, 1, 1 }, 0, GRID_FLAG_PADDING, 8, 8, 0
+	{ { 0 }, 0, 0, 0 }, 0, GRID_FLAG_PADDING, 8, 8, 0
 };
 
 struct screen_write_collect_item {
diff --git a/tmux.h b/tmux.h
index 83e2ed45..f0e6ee8b 100644
--- a/tmux.h
+++ b/tmux.h
@@ -2904,7 +2904,7 @@ u_int		 session_group_attached_count(struct session_group *);
 void		 session_renumber_windows(struct session *);
 
 /* utf8.c */
-utf8_char	 utf8_build_one(char, u_int);
+utf8_char	 utf8_build_one(u_char);
 enum utf8_state	 utf8_from_data(const struct utf8_data *, utf8_char *);
 void		 utf8_to_data(utf8_char, struct utf8_data *);
 void		 utf8_set(struct utf8_data *, u_char);
diff --git a/utf8.c b/utf8.c
index e03d9e6e..44813ac9 100644
--- a/utf8.c
+++ b/utf8.c
@@ -55,19 +55,26 @@ union utf8_map {
 	utf8_char	uc;
 	struct {
 		u_char	flags;
-#define UTF8_FLAG_SIZE 0x1f
-#define UTF8_FLAG_WIDTH2 0x20
-
 		u_char	data[3];
 	};
 } __packed;
 
+#define UTF8_GET_SIZE(flags) ((flags) & 0x1f)
+#define UTF8_GET_WIDTH(flags) (((flags) >> 5) - 1)
+
+#define UTF8_SET_SIZE(size) (size)
+#define UTF8_SET_WIDTH(width) ((width + 1) << 5)
+
+static const union utf8_map utf8_space0 = {
+	.flags = UTF8_SET_WIDTH(0)|UTF8_SET_SIZE(0),
+	.data = ""
+};
 static const union utf8_map utf8_space1 = {
-	.flags = 1,
+	.flags = UTF8_SET_WIDTH(1)|UTF8_SET_SIZE(1),
 	.data = " "
 };
 static const union utf8_map utf8_space2 = {
-	.flags = UTF8_FLAG_WIDTH2|2,
+	.flags = UTF8_SET_WIDTH(2)|UTF8_SET_SIZE(2),
 	.data = "  "
 };
 
@@ -134,24 +141,12 @@ utf8_from_data(const struct utf8_data *ud, utf8_char *uc)
 	union utf8_map	 m = { .uc = 0 };
 	u_int		 offset;
 
-	if (ud->width == 0)
-		goto fail;
-	if (ud->width != 1 && ud->width != 2)
+	if (ud->width > 2)
 		fatalx("invalid UTF-8 width");
-	if (ud->size == 0)
-		fatalx("invalid UTF-8 size");
 
-	if (ud->size > UTF8_FLAG_SIZE)
+	if (ud->size > UTF8_SIZE)
 		goto fail;
-	if (ud->size == 1) {
-		*uc = utf8_build_one(ud->data[0], 1);
-		return (UTF8_DONE);
-	}
-
-	m.flags = ud->size;
-	if (ud->width == 2)
-		m.flags |= UTF8_FLAG_WIDTH2;
-
+	m.flags = UTF8_SET_SIZE(ud->size)|UTF8_SET_WIDTH(ud->width);
 	if (ud->size <= 3)
 		memcpy(m.data, ud->data, ud->size);
 	else {
@@ -165,7 +160,9 @@ utf8_from_data(const struct utf8_data *ud, utf8_char *uc)
 	return (UTF8_DONE);
 
 fail:
-	if (ud->width == 1)
+	if (ud->width == 0)
+		*uc = htonl(utf8_space0.uc);
+	else if (ud->width == 1)
 		*uc = htonl(utf8_space1.uc);
 	else
 		*uc = htonl(utf8_space2.uc);
@@ -181,11 +178,8 @@ utf8_to_data(utf8_char uc, struct utf8_data *ud)
 	u_int			 offset;
 
 	memset(ud, 0, sizeof *ud);
-	ud->size = ud->have = (m.flags & UTF8_FLAG_SIZE);
-	if (m.flags & UTF8_FLAG_WIDTH2)
-		ud->width = 2;
-	else
-		ud->width = 1;
+	ud->size = ud->have = UTF8_GET_SIZE(m.flags);
+	ud->width = UTF8_GET_WIDTH(m.flags);
 
 	if (ud->size <= 3) {
 		memcpy(ud->data, m.data, ud->size);
@@ -203,12 +197,12 @@ utf8_to_data(utf8_char uc, struct utf8_data *ud)
 
 /* Get UTF-8 character from a single ASCII character. */
 u_int
-utf8_build_one(char c, u_int width)
+utf8_build_one(u_char ch)
 {
-	union utf8_map	m = { .flags = 1, .data[0] = c };
+	union utf8_map	m;
 
-	if (width == 2)
-		m.flags |= UTF8_FLAG_WIDTH2;
+	m.flags = UTF8_SET_SIZE(1)|UTF8_SET_WIDTH(1);
+	m.data[0] = ch;
 	return (htonl(m.uc));
 }
 
diff --git a/window-copy.c b/window-copy.c
index af80186b..20f351aa 100644
--- a/window-copy.c
+++ b/window-copy.c
@@ -3628,6 +3628,8 @@ window_copy_get_selection(struct window_mode_entry *wme, size_t *len)
 		buf = window_copy_match_at_cursor(data);
 		if (buf != NULL)
 			*len = strlen(buf);
+		else
+			*len = 0;
 		return (buf);
 	}
 
@@ -3719,6 +3721,7 @@ window_copy_get_selection(struct window_mode_entry *wme, size_t *len)
 	/* Don't bother if no data. */
 	if (off == 0) {
 		free(buf);
+		*len = 0;
 		return (NULL);
 	}
 	if (keys == MODEKEY_EMACS || lastex <= ey_last)
@@ -3753,9 +3756,6 @@ window_copy_copy_pipe(struct window_mode_entry *wme, struct session *s,
 	struct job	*job;
 
 	buf = window_copy_get_selection(wme, &len);
-	if (buf == NULL)
-		return;
-
 	if (cmd == NULL || *cmd == '\0')
 		cmd = options_get_string(global_options, "copy-command");
 	if (cmd != NULL && *cmd != '\0') {
@@ -3763,7 +3763,8 @@ window_copy_copy_pipe(struct window_mode_entry *wme, struct session *s,
 		    -1, -1);
 		bufferevent_write(job_get_event(job), buf, len);
 	}
-	window_copy_copy_buffer(wme, prefix, buf, len);
+	if (buf != NULL)
+		window_copy_copy_buffer(wme, prefix, buf, len);
 }
 
 static void