diff --git a/0.73_My_PuTTY/putty.h b/0.73_My_PuTTY/putty.h
index 1b258bc..94adc58 100644
--- a/0.73_My_PuTTY/putty.h
+++ b/0.73_My_PuTTY/putty.h
@@ -1810,9 +1810,8 @@ int format_arrow_key(char *buf, Terminal *term, int xkey, int modifier, bool alt
 int format_arrow_key(char *buf, Terminal *term, int xkey, bool ctrl);
 #endif
 
-int format_function_key(char *buf, Terminal *term, int key_number,
-                        bool shift, bool ctrl);
-int format_small_keypad_key(char *buf, Terminal *term, SmallKeypadKey key);
+int format_function_key(char *buf, Terminal *term, int key_number, int modifier, bool alt);
+int format_small_keypad_key(char *buf, Terminal *term, SmallKeypadKey key, int modifier, bool alt);
 int format_numeric_keypad_key(char *buf, Terminal *term, char key,
                               bool shift, bool ctrl);
 
diff --git a/0.73_My_PuTTY/terminal.c b/0.73_My_PuTTY/terminal.c
index 1c37407..21ccc32 100644
--- a/0.73_My_PuTTY/terminal.c
+++ b/0.73_My_PuTTY/terminal.c
@@ -7150,6 +7150,18 @@ void term_mouse(Terminal *term, Mouse_Button braw, Mouse_Button bcooked,
     term_update(term);
 }
 
+int get_xterm_modifier(bool shift, bool ctrl, bool alt)
+{
+    int xterm_modifier = 1;  // no modifier key was pressed
+    if (shift)
+        xterm_modifier += 1;
+    if (alt)
+        xterm_modifier += 2;
+    if (ctrl)
+        xterm_modifier += 4;
+    return xterm_modifier;
+}
+
 #ifdef MOD_KEYMAPPING
 int format_arrow_key(char *buf, Terminal *term, int xkey, int modifier, bool alt)
 #else
@@ -7223,8 +7235,7 @@ int format_arrow_key(char *buf, Terminal *term, int xkey, bool ctrl)
     return p - buf;
 }
 
-int format_function_key(char *buf, Terminal *term, int key_number,
-                        bool shift, bool ctrl)
+int format_function_key(char *buf, Terminal *term, int key_number, int modifier, bool alt)
 {
     char *p = buf;
 
@@ -7237,6 +7248,37 @@ int format_function_key(char *buf, Terminal *term, int key_number,
     assert(key_number > 0);
     assert(key_number < lenof(key_number_to_tilde_code));
 
+    bool shift = modifier & 1;
+    bool ctrl = modifier & 2;
+    if (term->funky_type == FUNKY_XTERM && !term->vt52_mode)
+    {
+        // XTerm mode
+        char prefix[20];
+        char suffix[20];
+        int xterm_modifier = get_xterm_modifier(shift, ctrl, alt);
+        if (xterm_modifier > 1)
+        {
+            sprintf(prefix, "[1;%d", xterm_modifier);
+            sprintf(suffix, ";%d", xterm_modifier);
+        }
+        else
+        {
+            sprintf(prefix, "O");
+            sprintf(suffix, "");
+        }
+
+        int code = key_number_to_tilde_code[key_number];
+        if (code >= 11 && code <= 14)
+        {
+            p += sprintf(p, "\x1B%s%c", prefix, code + 'P' - 11);
+        }
+        else
+        {
+            p += sprintf(p, "\x1B[%d%s~", code, suffix);
+        }
+        return p - buf;
+    }
+
     int index = (shift && key_number <= 10) ? key_number + 10 : key_number;
     int code = key_number_to_tilde_code[index];
 
@@ -7273,7 +7315,7 @@ int format_function_key(char *buf, Terminal *term, int key_number,
     return p - buf;
 }
 
-int format_small_keypad_key(char *buf, Terminal *term, SmallKeypadKey key)
+int format_small_keypad_key(char *buf, Terminal *term, SmallKeypadKey key, int modifier, bool alt)
 {
     char *p = buf;
 
@@ -7288,6 +7330,37 @@ int format_small_keypad_key(char *buf, Terminal *term, SmallKeypadKey key)
       default: unreachable("bad small keypad key enum value");
     }
 
+    bool shift = modifier & 1;
+    bool ctrl = modifier & 2;
+    if (term->funky_type == FUNKY_XTERM && !term->vt52_mode)
+    {
+        // XTerm mode
+        char prefix[20];
+        char suffix[20];
+        int xterm_modifier = get_xterm_modifier(shift, ctrl, alt);
+        if (xterm_modifier > 1)
+        {
+            sprintf(prefix, "[1;%d", xterm_modifier);
+            sprintf(suffix, ";%d", xterm_modifier);
+        }
+        else
+        {
+            sprintf(prefix, "[");
+            sprintf(suffix, "");
+        }
+
+        if (code == 1 || code == 4)
+        {
+            p += sprintf(p, "\x1B%s%c", prefix, code == 1 ? 'H' : 'F');
+        }
+        else
+        {
+            p += sprintf(p, "\x1B[%d%s~", code, suffix);
+        }
+
+        return p - buf;
+    }
+
     /* Reorder edit keys to physical order */
     if (term->funky_type == FUNKY_VT400 && code <= 6)
         code = "\0\2\1\4\5\3\6"[code];
diff --git a/0.73_My_PuTTY/windows/window.c b/0.73_My_PuTTY/windows/window.c
index 6d75537..7c7868f 100644
--- a/0.73_My_PuTTY/windows/window.c
+++ b/0.73_My_PuTTY/windows/window.c
@@ -6591,7 +6591,7 @@ if( !get_param("PUTTY") && conf_get_int(conf, CONF_disablealtgr) ) {
 					break;
 				default:
 					break;
-			}			
+			}
 			if (!(term->funky_type == FUNKY_XTERM && !term->vt52_mode) || fkey == 0) {
 				*p++ = '\033';
 			}
@@ -6857,8 +6857,7 @@ if( !get_param("PUTTY") && conf_get_int(conf, CONF_disablealtgr) ) {
 	  case VK_F19: fkey_number = 19; goto numbered_function_key;
 	  case VK_F20: fkey_number = 20; goto numbered_function_key;
           numbered_function_key:
-            p += format_function_key((char *)p, term, fkey_number,
-                                     shift_state & 1, shift_state & 2);
+            p += format_function_key((char *)p, term, fkey_number, shift_state, left_alt);
             return p - output;
 
             SmallKeypadKey sk_key;