diff --git a/kitty/control-codes.h b/kitty/control-codes.h
index 75e17824c..04359cda4 100644
--- a/kitty/control-codes.h
+++ b/kitty/control-codes.h
@@ -70,6 +70,7 @@
 #define ESC_ST '\\'
 #define ESC_PM '^'
 #define ESC_APC '_'
+#define ESC_SOS 'X'
 
 // *Reset*.
 #define ESC_RIS 'c'
diff --git a/kitty/vt-parser.c b/kitty/vt-parser.c
index 188f43c34..ed1af8d03 100644
--- a/kitty/vt-parser.c
+++ b/kitty/vt-parser.c
@@ -158,7 +158,7 @@ static const int64_t digit_multipliers[] = {
 
 // Data structures {{{
 typedef enum VTEState {
-    VTE_NORMAL, VTE_ESC = ESC, VTE_CSI = ESC_CSI, VTE_OSC = ESC_OSC, VTE_DCS = ESC_DCS, VTE_APC = ESC_APC, VTE_PM = ESC_PM
+    VTE_NORMAL, VTE_ESC = ESC, VTE_CSI = ESC_CSI, VTE_OSC = ESC_OSC, VTE_DCS = ESC_DCS, VTE_APC = ESC_APC, VTE_PM = ESC_PM, VTE_SOS = ESC_SOS
 } VTEState;
 
 static inline const char*
@@ -171,6 +171,7 @@ vte_state_name(VTEState s) {
         case VTE_DCS: return "VTE_DCS";
         case VTE_APC: return "VTE_APC";
         case VTE_PM: return "VTE_PM";
+        case VTE_SOS: return "VTE_SOS";
     }
     static char buf[16];
     snprintf(buf, sizeof(buf), "VTE_0x%x", s);
@@ -269,6 +270,7 @@ consume_esc(PS *self) {
             case ESC_OSC: SET_STATE(OSC); break;
             case ESC_CSI: SET_STATE(CSI); reset_csi(&self->csi); break;
             case ESC_APC: SET_STATE(APC); break;
+            case ESC_SOS: SET_STATE(SOS); break;
             case ESC_PM: SET_STATE(PM); break;
             IS_ESCAPED_CHAR:
                 return false;
@@ -1344,6 +1346,20 @@ dispatch_pm(PS *self UNUSED, uint8_t *buf, size_t bufsz, bool is_extended UNUSED
 }
 
 
+// }}}
+
+// SOS mode {{{
+static void
+dispatch_sos(PS *self UNUSED, uint8_t *buf, size_t bufsz, bool is_extended UNUSED) {
+    if (bufsz < 2) return;
+    switch(buf[0]) {
+        default:
+            REPORT_ERROR("Unrecognized SOS code: 0x%x", buf[0]);
+            break;
+    }
+}
+
+
 // }}}
 
 // Parse loop {{{
@@ -1373,6 +1389,8 @@ consume_input(PS *self, PyObject *dump_callback UNUSED, id_type window_id UNUSED
             consume(pm);
         case VTE_DCS:
             consume(dcs);
+        case VTE_SOS:
+            consume(sos);
     }
 
 #ifdef DUMP_COMMANDS
diff --git a/kitty_tests/parser.py b/kitty_tests/parser.py
index 6afb23a80..a091191f5 100644
--- a/kitty_tests/parser.py
+++ b/kitty_tests/parser.py
@@ -630,6 +630,7 @@ class TestParser(BaseTest):
         pb = partial(self.parse_bytes_dump, s)
         pb('a\033_+\\+\033\\bcde', ('draw', 'a'), ('Unrecognized APC code: 0x2b',), ('draw', 'bcde'))
         pb('a\033^+\\+\033\\bcde', ('draw', 'a'), ('Unrecognized PM code: 0x2b',), ('draw', 'bcde'))
+        pb('a\033X+\\+\033\\bcde', ('draw', 'a'), ('Unrecognized SOS code: 0x2b',), ('draw', 'bcde'))
 
     def test_graphics_command(self):
         from base64 import standard_b64encode