diff --git a/kitty/modes.h b/kitty/modes.h
index b55b3d8b5..e87334f8c 100644
--- a/kitty/modes.h
+++ b/kitty/modes.h
@@ -76,8 +76,5 @@
 #define BRACKETED_PASTE_START "200~"
 #define BRACKETED_PASTE_END  "201~"
 
-// Styled underlines
-#define STYLED_UNDERLINES (2016 << 5)
-
 // Extended keyboard protocol
 #define EXTENDED_KEYBOARD (2017 << 5)
diff --git a/kitty/screen.c b/kitty/screen.c
index 9abd80dd6..65b4cc48e 100644
--- a/kitty/screen.c
+++ b/kitty/screen.c
@@ -1102,8 +1102,6 @@ report_mode_status(Screen *self, unsigned int which, bool private) {
         KNOWN_MODE(EXTENDED_KEYBOARD);
         KNOWN_MODE(FOCUS_TRACKING);
 #undef KNOWN_MODE
-        case STYLED_UNDERLINES:
-            ans = 3; break;
     }
     int sz = snprintf(buf, sizeof(buf) - 1, "%s%u;%u$y", (private ? "?" : ""), which, ans);
     if (sz > 0) write_escape_code_to_child(self, CSI, buf);
diff --git a/kitty_tests/parser.py b/kitty_tests/parser.py
index 7f2691f28..1ded651f1 100644
--- a/kitty_tests/parser.py
+++ b/kitty_tests/parser.py
@@ -160,9 +160,6 @@ class TestParser(BaseTest):
         pb('\033[?1l', ('screen_reset_mode', 1, 1))
         self.assertFalse(s.cursor_key_mode)
         c.clear()
-        pb('\033[?2016$p', ('report_mode_status', 2016, 1))
-        self.ae(c.wtcbuf, b'\033[?2016;3$y')
-        c.clear()
         pb('\033[?1$p', ('report_mode_status', 1, 1))
         self.ae(c.wtcbuf, b'\033[?1;2$y')
         pb('\033[2;4r', ('screen_set_margins', 2, 4))
diff --git a/protocol-extensions.asciidoc b/protocol-extensions.asciidoc
index d4a8fb684..6719f1a52 100644
--- a/protocol-extensions.asciidoc
+++ b/protocol-extensions.asciidoc
@@ -54,23 +54,6 @@ To reset the underline color (also previously reserved and unused):
 <ESC>[59m
 ```
 
-A client can query if the terminal emulator supports this underline extension using the
-standard link:http://vt100.net/docs/vt510-rm/DECRQM[DECRQM] escape sequence, with the
-mode value `2016`, like this:
-
-Client sends:
-
-```
-<ESC>[?2016$p
-```
-
-If the terminal supports this underline extension, it must respond with
-link:http://vt100.net/docs/vt510-rm/DECRPM[DECRPM]
-
-```
-<ESC>[?2016;3$p
-```
-
 
 == Graphics rendering