diff --git a/mysql-test/r/innodb_ext_key.result b/mysql-test/r/innodb_ext_key.result
index c7a5b1a80ca..880d7a8bceb 100644
--- a/mysql-test/r/innodb_ext_key.result
+++ b/mysql-test/r/innodb_ext_key.result
@@ -790,3 +790,19 @@ EXPLAIN
 }
 drop table t1;
 SET optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+#
+# MDEV-11172: EXPLAIN shows non-sensical value for key_len with type=index
+#
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+CREATE TABLE t2 (
+pk VARCHAR(50),
+a VARCHAR(20),
+KEY k1(a),
+PRIMARY KEY(pk)
+)ENGINE=INNODB;
+INSERT INTO t2 SELECT a,a FROM t1;
+EXPLAIN SELECT pk FROM t2 FORCE INDEX(k1);
+id	select_type	table	type	possible_keys	key	key_len	ref	rows	Extra
+1	SIMPLE	t2	index	NULL	k1	23	NULL	10	Using index
+DROP TABLE t1,t2;
diff --git a/mysql-test/t/innodb_ext_key.test b/mysql-test/t/innodb_ext_key.test
index f5edd736490..de9ca10ff1b 100644
--- a/mysql-test/t/innodb_ext_key.test
+++ b/mysql-test/t/innodb_ext_key.test
@@ -606,3 +606,22 @@ explain format= json
 select * from t1 force index(k1)  where f2 <= 5 and pk2 <=5 and pk1 = 'abc' and f1 <= '3';
 drop table t1;
 SET optimizer_use_condition_selectivity=@save_optimizer_use_condition_selectivity;
+
+--echo #
+--echo # MDEV-11172: EXPLAIN shows non-sensical value for key_len with type=index
+--echo #
+
+CREATE TABLE t1(a INT);
+INSERT INTO t1 VALUES (0),(1),(2),(3),(4),(5),(6),(7),(8),(9);
+
+CREATE TABLE t2 (
+  pk VARCHAR(50),
+  a VARCHAR(20),
+  KEY k1(a),
+  PRIMARY KEY(pk)
+)ENGINE=INNODB;
+
+INSERT INTO t2 SELECT a,a FROM t1;
+EXPLAIN SELECT pk FROM t2 FORCE INDEX(k1);
+
+DROP TABLE t1,t2;
diff --git a/sql/structs.h b/sql/structs.h
index 67fb0d5dd66..27b9725815b 100644
--- a/sql/structs.h
+++ b/sql/structs.h
@@ -90,7 +90,7 @@ class engine_option_value;
 struct ha_index_option_struct;
 
 typedef struct st_key {
-  uint	key_length;			/* Tot length of key */
+  uint	key_length;			/* total length of user defined key parts  */
   ulong flags;                          /* dupp key and pack flags */
   uint	user_defined_key_parts;	   /* How many key_parts */
   uint	usable_key_parts; /* Should normally be = user_defined_key_parts */
diff --git a/sql/table.cc b/sql/table.cc
index e4492f21a30..1004f583448 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -2273,6 +2273,12 @@ int TABLE_SHARE::init_from_binary_frm_image(THD *thd, bool write,
           key_part->null_bit= field->null_bit;
           key_part->store_length+=HA_KEY_NULL_LENGTH;
           keyinfo->flags|=HA_NULL_PART_KEY;
+
+          /*
+            This branch is executed only for user defined key parts of the
+            secondary indexes.
+          */
+          DBUG_ASSERT(i < keyinfo->user_defined_key_parts);
           keyinfo->key_length+= HA_KEY_NULL_LENGTH;
         }
         if (field->type() == MYSQL_TYPE_BLOB ||
@@ -2285,7 +2291,8 @@ int TABLE_SHARE::init_from_binary_frm_image(THD *thd, bool write,
           else
             key_part->key_part_flag|= HA_VAR_LENGTH_PART;
           key_part->store_length+=HA_KEY_BLOB_LENGTH;
-          keyinfo->key_length+= HA_KEY_BLOB_LENGTH;
+          if (i < keyinfo->user_defined_key_parts)
+            keyinfo->key_length+= HA_KEY_BLOB_LENGTH;
         }
         if (field->type() == MYSQL_TYPE_BIT)
           key_part->key_part_flag|= HA_BIT_PART;
@@ -2378,7 +2385,6 @@ int TABLE_SHARE::init_from_binary_frm_image(THD *thd, bool write,
 
       set_if_bigger(share->max_key_length,keyinfo->key_length+
                     keyinfo->user_defined_key_parts);
-      share->total_key_length+= keyinfo->key_length;
       /*
         MERGE tables do not have unique indexes. But every key could be
         an unique index on the underlying MyISAM table. (Bug #10400)
diff --git a/sql/table.h b/sql/table.h
index a5d412c2c08..83c72f76831 100644
--- a/sql/table.h
+++ b/sql/table.h
@@ -773,7 +773,7 @@ struct TABLE_SHARE
   uint rec_buff_length;                 /* Size of table->record[] buffer */
   uint keys, key_parts;
   uint ext_key_parts;       /* Total number of key parts in extended keys */
-  uint max_key_length, max_unique_length, total_key_length;
+  uint max_key_length, max_unique_length;
   uint uniques;                         /* Number of UNIQUE index */
   uint db_create_options;		/* Create options from database */
   uint db_options_in_use;		/* Options in use */