diff --git a/window-copy.c b/window-copy.c
index ec6a2f4e..9a0179a4 100644
--- a/window-copy.c
+++ b/window-copy.c
@@ -3148,6 +3148,11 @@ window_copy_cellstring(const struct grid_line *gl, u_int px, size_t *size,
 	}
 
 	utf8_to_data(gl->extddata[gce->offset].data, &ud);
+	if (ud.size == 0) {
+		*size = 0;
+		*allocated = 0;
+		return (NULL);
+	}
 	*size = ud.size;
 	*allocated = 1;