diff --git a/rslib/src/notes.rs b/rslib/src/notes.rs
index 6021cb3e5..23e9f7019 100644
--- a/rslib/src/notes.rs
+++ b/rslib/src/notes.rs
@@ -24,8 +24,6 @@ use std::{
 
 define_newtype!(NoteID, i64);
 
-// fixme: ensure nulls and x1f not in field contents
-
 #[derive(Default)]
 pub(crate) struct TransformNoteOutput {
     pub changed: bool,
@@ -88,6 +86,12 @@ impl Note {
             )));
         }
 
+        for field in &mut self.fields {
+            if field.contains(invalid_char_for_field) {
+                *field = field.replace(invalid_char_for_field, "");
+            }
+        }
+
         if normalize_text {
             for field in &mut self.fields {
                 ensure_string_in_nfc(field);
@@ -226,6 +230,10 @@ fn anki_base91(mut n: u64) -> String {
     buf.chars().rev().collect()
 }
 
+fn invalid_char_for_field(c: char) -> bool {
+    c.is_ascii_control() && c != '\n' && c != '\t'
+}
+
 impl Collection {
     fn canonify_note_tags(&self, note: &mut Note, usn: Usn) -> Result<()> {
         if !note.tags.is_empty() {