diff --git a/CHANGELOG.md b/CHANGELOG.md
index 242f3bab..f9c665fa 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -74,6 +74,8 @@
 * Use `utf8proc_charwidth()` instead of `wcwidth()`+`wcswidth()` when
   calculating character width, when foot has been built with utf8proc
   support ([#1865][1865]).
+* Run-time changes to the window title, and the app ID now require the
+  new value to consist of printable characters only.
 
 [1865]: https://codeberg.org/dnkl/foot/issues/1865
 
diff --git a/misc.c b/misc.c
index 1e5b9328..c7abe03b 100644
--- a/misc.c
+++ b/misc.c
@@ -44,8 +44,19 @@ timespec_sub(const struct timespec *a, const struct timespec *b,
 }
 
 bool
-is_valid_utf8(const char *value)
+is_valid_utf8_and_printable(const char *value)
 {
-    return value != NULL &&
-           mbsntoc32(NULL, value, strlen(value), 0) != (size_t)-1;
+    char32_t *wide = ambstoc32(value);
+    if (wide == NULL)
+        return false;
+
+    for (const char32_t *c = wide; *c != U'\0'; c++) {
+        if (!isc32print(*c)) {
+            free(wide);
+            return false;
+        }
+    }
+
+    free(wide);
+    return true;
 }
diff --git a/misc.h b/misc.h
index cce8d2c1..6c77c484 100644
--- a/misc.h
+++ b/misc.h
@@ -9,4 +9,4 @@ bool isword(char32_t wc, bool spaces_only, const char32_t *delimiters);
 void timespec_add(const struct timespec *a, const struct timespec *b, struct timespec *res);
 void timespec_sub(const struct timespec *a, const struct timespec *b, struct timespec *res);
 
-bool is_valid_utf8(const char *value);
+bool is_valid_utf8_and_printable(const char *value);
diff --git a/terminal.c b/terminal.c
index 5532972e..a4963bc8 100644
--- a/terminal.c
+++ b/terminal.c
@@ -3570,7 +3570,7 @@ term_set_window_title(struct terminal *term, const char *title)
     if (term->window_title != NULL && streq(term->window_title, title))
         return;
 
-    if (!is_valid_utf8(title)) {
+    if (!is_valid_utf8_and_printable(title)) {
         /* It's an xdg_toplevel::set_title() protocol violation to set
            a title with an invalid UTF-8 sequence */
         LOG_WARN("%s: title is not valid UTF-8, ignoring", title);
@@ -3593,7 +3593,7 @@ term_set_app_id(struct terminal *term, const char *app_id)
     if (term->app_id != NULL && app_id != NULL && streq(term->app_id, app_id))
         return;
 
-    if (app_id != NULL && !is_valid_utf8(app_id)) {
+    if (app_id != NULL && !is_valid_utf8_and_printable(app_id)) {
         LOG_WARN("%s: app-id is not valid UTF-8, ignoring", app_id);
         return;
     }