diff --git a/tccpp.c b/tccpp.c
index 4d5169e..48e3501 100644
--- a/tccpp.c
+++ b/tccpp.c
@@ -2105,6 +2105,43 @@ static void parse_escape_string(CString *outstr, const uint8_t *buf, int is_long
                     tcc_warning("unknown escape sequence: \'\\x%x\'", c);
                 break;
             }
+        } else if (is_long && c >= 0x80) {
+            /* assume we are processing UTF-8 sequence */
+
+            int cont; /* count of continuation bytes */
+            int i;
+
+            /* decode leading byte */
+            if ((c >> 5) == 0x6) {
+                cont = 1; n = c & 0x1f;
+            } else if ((c >> 4) == 0xe) {
+                cont = 2; n = c & 0xf;
+            } else if ((c >> 3) == 0x1e) {
+                cont = 3; n = c & 0x7;
+            } else {
+                goto invalid_utf8_sequence;
+            }
+
+            /* decode continuation bytes */
+            for (i = 1; i <= cont; i++) {
+                if ((p[i] >> 6) != 2)
+                    goto invalid_utf8_sequence;
+                n = (n << 6) | (p[i] & 0x3f);
+            }
+
+            /* check for overlong encoding */
+            if ((cont == 1 && n < 0x80) ||
+                (cont == 2 && n < 0x800) ||
+                (cont == 3 && n < 0x10000))
+               goto invalid_utf8_sequence;
+
+            /* advance pointer */
+            p += 1 + cont;
+            c = n;
+            goto add_char_nonext;
+
+        invalid_utf8_sequence:
+            tcc_warning("invalid UTF-8 sequence");
         }
         p++;
     add_char_nonext: