diff --git a/mysql-test/r/ctype_utf8mb4.result b/mysql-test/r/ctype_utf8mb4.result
index d43f3b0e0bd..4de7a192546 100644
--- a/mysql-test/r/ctype_utf8mb4.result
+++ b/mysql-test/r/ctype_utf8mb4.result
@@ -2438,6 +2438,9 @@ t1	CREATE TABLE `t1` (
 INSERT INTO t1(subject) VALUES ('abcd');
 INSERT INTO t1(subject) VALUES(x'f0909080');
 DROP TABLE t1;
+CREATE TABLE t1 (a TEXT CHARACTER SET utf8mb4, FULLTEXT INDEX(a));
+INSERT INTO t1 VALUES (0xF0A08080 /* U+20000 */ );
+DROP TABLE t1;
 #
 # Bug #51676 Server crashes on SELECT, ORDER BY on 'utf8mb4' column
 #
diff --git a/mysql-test/t/ctype_utf8mb4.test b/mysql-test/t/ctype_utf8mb4.test
index 8916de670c1..f396d36e5b0 100644
--- a/mysql-test/t/ctype_utf8mb4.test
+++ b/mysql-test/t/ctype_utf8mb4.test
@@ -1763,6 +1763,13 @@ INSERT INTO t1(subject) VALUES ('abcd');
 INSERT INTO t1(subject) VALUES(x'f0909080');
 DROP TABLE t1;
 
+#
+# Make sure fulltext does not crash on supplementary characters
+#
+CREATE TABLE t1 (a TEXT CHARACTER SET utf8mb4, FULLTEXT INDEX(a));
+INSERT INTO t1 VALUES (0xF0A08080 /* U+20000 */ );
+DROP TABLE t1;
+
 --echo #
 --echo # Bug #51676 Server crashes on SELECT, ORDER BY on 'utf8mb4' column
 --echo #
diff --git a/strings/ctype-mb.c b/strings/ctype-mb.c
index 98b598c3c2c..b1b381da59e 100644
--- a/strings/ctype-mb.c
+++ b/strings/ctype-mb.c
@@ -1123,8 +1123,16 @@ size_t my_numcells_mb(CHARSET_INFO *cs, const char *b, const char *e)
       continue;
     }
     b+= mb_len;
-    pg= (wc >> 8) & 0xFF;
-    clen+= utr11_data[pg].p ? utr11_data[pg].p[wc & 0xFF] : utr11_data[pg].page;
+    if (wc > 0xFFFF)
+    {
+      if (wc >= 0x20000 && wc <= 0x3FFFD) /* CJK Ideograph Extension B, C */
+        clen+= 1;
+    }
+    else
+    {
+      pg= (wc >> 8) & 0xFF;
+      clen+= utr11_data[pg].p ? utr11_data[pg].p[wc & 0xFF] : utr11_data[pg].page;
+    }
     clen++;
   }
   return clen;
@@ -1136,7 +1144,7 @@ int my_mb_ctype_mb(CHARSET_INFO *cs, int *ctype,
 {
   my_wc_t wc;
   int res= cs->cset->mb_wc(cs, &wc, s, e);
-  if (res <= 0)
+  if (res <= 0 || wc > 0xFFFF)
     *ctype= 0;
   else
     *ctype= my_uni_ctype[wc>>8].ctype ?