diff --git a/kitty/options/to-c.h b/kitty/options/to-c.h
index 8e2ce4bf4..5c8126ae4 100644
--- a/kitty/options/to-c.h
+++ b/kitty/options/to-c.h
@@ -124,22 +124,28 @@ url_prefixes(PyObject *up, Options *opts) {
     }
 }
 
+static char_type*
+list_of_chars(PyObject *chars) {
+    if (!PyUnicode_Check(chars)) { PyErr_SetString(PyExc_TypeError, "list_of_chars must be a string"); return NULL; }
+    char_type *ans = calloc(PyUnicode_GET_LENGTH(chars) + 1, sizeof(char_type));
+    if (ans) {
+        for (ssize_t i = 0; i < PyUnicode_GET_LENGTH(chars); i++) {
+            ans[i] = PyUnicode_READ(PyUnicode_KIND(chars), PyUnicode_DATA(chars), i);
+        }
+    }
+    return ans;
+}
+
 static void
 url_excluded_characters(PyObject *chars, Options *opts) {
-    if (!PyUnicode_Check(chars)) { PyErr_SetString(PyExc_TypeError, "url_excluded_characters must be a string"); return; }
-    for (size_t i = 0; i < MIN((size_t)PyUnicode_GET_LENGTH(chars), arraysz(opts->url_excluded_characters)); i++) {
-        opts->url_excluded_characters[i] = PyUnicode_READ(PyUnicode_KIND(chars), PyUnicode_DATA(chars), i);
-    }
-    opts->url_excluded_characters_count = PyUnicode_GET_LENGTH(chars);
+    free(opts->url_excluded_characters);
+    opts->url_excluded_characters = list_of_chars(chars);
 }
 
 static void
 select_by_word_characters(PyObject *chars, Options *opts) {
-    if (!PyUnicode_Check(chars)) { PyErr_SetString(PyExc_TypeError, "select_by_word_characters must be a string"); return; }
-    for (size_t i = 0; i < MIN((size_t)PyUnicode_GET_LENGTH(chars), arraysz(opts->select_by_word_characters)); i++) {
-        opts->select_by_word_characters[i] = PyUnicode_READ(PyUnicode_KIND(chars), PyUnicode_DATA(chars), i);
-    }
-    opts->select_by_word_characters_count = PyUnicode_GET_LENGTH(chars);
+    free(opts->select_by_word_characters);
+    opts->select_by_word_characters = list_of_chars(chars);
 }
 
 static void
diff --git a/kitty/screen.c b/kitty/screen.c
index 90b7c8df1..f7f83fa6a 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -2563,8 +2563,10 @@ screen_selection_range_for_line(Screen *self, index_type y, index_type *start, i
 
 static inline bool
 is_opt_word_char(char_type ch) {
-    for (size_t i = 0; i < OPT(select_by_word_characters_count); i++) {
-        if (OPT(select_by_word_characters[i]) == ch) return true;
+    if (OPT(select_by_word_characters)) {
+        for (const char_type *p = OPT(select_by_word_characters); *p; p++) {
+            if (ch == *p) return true;
+        }
     }
     return false;
 }
diff --git a/kitty/state.c b/kitty/state.c
index 99febdfc5..ba0d6e56c 100644
--- a/kitty/state.c
+++ b/kitty/state.c
@@ -1091,6 +1091,8 @@ finalize(void) {
     free_bgimage(&global_state.bgimage, false);
     global_state.bgimage = NULL;
     free_url_prefixes();
+    free(OPT(select_by_word_characters)); OPT(select_by_word_characters) = NULL;
+    free(OPT(url_excluded_characters)); OPT(url_excluded_characters) = NULL;
 }
 
 bool
diff --git a/kitty/state.h b/kitty/state.h
index 84a4463f8..698695cc2 100644
--- a/kitty/state.h
+++ b/kitty/state.h
@@ -30,7 +30,7 @@ typedef struct {
     unsigned int url_style;
     unsigned int scrollback_pager_history_size;
     bool scrollback_fill_enlarged_window;
-    char_type select_by_word_characters[256]; size_t select_by_word_characters_count;
+    char_type *select_by_word_characters;
     color_type url_color, background, foreground, active_border_color, inactive_border_color, bell_border_color;
     color_type mark1_foreground, mark1_background, mark2_foreground, mark2_background, mark3_foreground, mark3_background;
     monotonic_t repaint_delay, input_delay;
@@ -70,7 +70,7 @@ typedef struct {
         UrlPrefix *values;
         size_t num, max_prefix_len;
     } url_prefixes;
-    char_type url_excluded_characters[256]; size_t url_excluded_characters_count;
+    char_type *url_excluded_characters;
     bool detect_urls;
     bool tab_bar_hidden;
     double font_size;
diff --git a/kitty/unicode-data.h b/kitty/unicode-data.h
index 89fe8605a..54e31ab92 100644
--- a/kitty/unicode-data.h
+++ b/kitty/unicode-data.h
@@ -14,8 +14,10 @@ combining_type mark_for_codepoint(char_type c);
 
 static inline bool
 is_excluded_from_url(uint32_t ch) {
-    for (size_t i = 0; i < OPT(url_excluded_characters_count); i++) {
-        if (ch == OPT(url_excluded_characters)[i]) return true;
+    if (OPT(url_excluded_characters)) {
+        for (const char_type *p = OPT(url_excluded_characters); *p; p++) {
+            if (ch == *p) return true;
+        }
     }
     return false;
 }