1 files changed, 8 insertions, 2 deletions

diff --git a/src/coding.c b/src/coding.c
index e779197bbde..ad2042672b2 100644
--- a/src/coding.c
+++ b/src/coding.c
@@ -493,6 +493,8 @@ enum iso_code_class_type
 
 #define CODING_ISO_FLAG_USE_OLDJIS      0x10000
 
+#define CODING_ISO_FLAG_LEVEL_4         0x20000
+
 #define CODING_ISO_FLAG_FULL_SUPPORT    0x100000
 
 /* A character to be produced on output if encoding of the original
@@ -3733,7 +3735,9 @@ decode_coding_iso_2022 (struct coding_system *coding)
               else
                 charset = CHARSET_FROM_ID (charset_id_2);
               ONE_MORE_BYTE (c1);
-              if (c1 < 0x20 || (c1 >= 0x80 && c1 < 0xA0))
+              if (c1 < 0x20 || (c1 >= 0x80 && c1 < 0xA0)
+                  || ((CODING_ISO_FLAGS (coding) & CODING_ISO_FLAG_LEVEL_4)
+                      ? c1 >= 0x80 : c1 < 0x80))
                 goto invalid_code;
               break;
 
@@ -3747,7 +3751,9 @@ decode_coding_iso_2022 (struct coding_system *coding)
               else
                 charset = CHARSET_FROM_ID (charset_id_3);
               ONE_MORE_BYTE (c1);
-              if (c1 < 0x20 || (c1 >= 0x80 && c1 < 0xA0))
+              if (c1 < 0x20 || (c1 >= 0x80 && c1 < 0xA0)
+                  || ((CODING_ISO_FLAGS (coding) & CODING_ISO_FLAG_LEVEL_4)
+                      ? c1 >= 0x80 : c1 < 0x80))
                 goto invalid_code;
               break;