diff --git a/pycodestyle.py b/pycodestyle.py
index f5e05cfa..4a973724 100755
--- a/pycodestyle.py
+++ b/pycodestyle.py
@@ -2010,6 +2010,11 @@ def build_tokens_line(self):
                 continue
             if token_type == tokenize.STRING:
                 text = mute_string(text)
+            elif (
+                    sys.version_info >= (3, 12) and
+                    token_type == tokenize.FSTRING_MIDDLE
+            ):
+                text = 'x' * len(text)
             if prev_row:
                 (start_row, start_col) = start
                 if prev_row != start_row:    # different row
diff --git a/testsuite/python36.py b/testsuite/python36.py
new file mode 100644
index 00000000..94ec2dc5
--- /dev/null
+++ b/testsuite/python36.py
@@ -0,0 +1,2 @@
+#: Okay
+f'{hello}:{world}'