diff --git a/kitty/data-types.h b/kitty/data-types.h
index 758ffcab7..6345a2d6e 100644
--- a/kitty/data-types.h
+++ b/kitty/data-types.h
@@ -59,6 +59,7 @@ static inline PyObject* Py_XNewRef(PyObject *o) { Py_XINCREF(o); return o; }
 
 typedef unsigned long long id_type;
 typedef uint32_t char_type;
+static_assert(sizeof(Py_UCS4) == sizeof(char_type), "PyUCS4 and char_type dont match");
 #define MAX_CHAR_TYPE_VALUE UINT32_MAX
 typedef uint32_t color_type;
 typedef uint16_t hyperlink_id_type;
diff --git a/kitty/line.c b/kitty/line.c
index 25ce85a36..1bebc7a78 100644
--- a/kitty/line.c
+++ b/kitty/line.c
@@ -229,7 +229,10 @@ static size_t
 cell_as_unicode(ListOfChars *lc, bool include_cc, Py_UCS4 *buf, char_type zero_char) {
     size_t n = 1;
     buf[0] = lc->chars[0] ? lc->chars[0] : zero_char;
-    if (include_cc && lc->count > 1) memcpy(buf + 1, lc->chars + 1, lc->count - 1);
+    if (include_cc && lc->count > 1) {
+        memcpy(buf + 1, lc->chars + 1, (lc->count - 1) * sizeof(lc->chars[0]));
+        n += lc->count - 1;
+    }
     return n;
 }