diff --git a/mysql-test/main/long_unique_bugs.result b/mysql-test/main/long_unique_bugs.result
index e5c14afd9c400..30ba3d0af9a73 100644
--- a/mysql-test/main/long_unique_bugs.result
+++ b/mysql-test/main/long_unique_bugs.result
@@ -651,5 +651,14 @@ f1	f2	f3	f4	f5	f6	f7
 4	00004	0001009089999		netstes	psit	e
 drop table t1;
 #
+# MDEV-29954 Unique hash key on column prefix is computed incorrectly
+#
+create table t1 (c char(10),unique key a using hash (c(1)));
+insert into t1 values (0);
+check table t1 extended;
+Table	Op	Msg_type	Msg_text
+test.t1	check	status	OK
+drop table t1;
+#
 # End of 10.5 tests
 #
diff --git a/mysql-test/main/long_unique_bugs.test b/mysql-test/main/long_unique_bugs.test
index 5fed7c72d9a26..12367b1deb8ce 100644
--- a/mysql-test/main/long_unique_bugs.test
+++ b/mysql-test/main/long_unique_bugs.test
@@ -634,6 +634,14 @@ replace t1 (f2, f3, f4, f5, f6, f7) values ('00004', '0001009089999', '', 'netst
 select * from t1;
 drop table t1;
 
+--echo #
+--echo # MDEV-29954 Unique hash key on column prefix is computed incorrectly
+--echo #
+create table t1 (c char(10),unique key a using hash (c(1)));
+insert into t1 values (0);
+check table t1 extended;
+drop table t1;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #
diff --git a/sql/field.cc b/sql/field.cc
index 9e1e0931ef134..fc828dcc86c88 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -7566,6 +7566,19 @@ int Field_string::cmp(const uchar *a_ptr, const uchar *b_ptr) const
 }
 
 
+int Field_string::cmp_prefix(const uchar *a_ptr, const uchar *b_ptr,
+                             size_t prefix_char_len) const
+{
+  size_t field_len= table->field[field_index]->field_length;
+
+  return field_charset()->coll->strnncollsp_nchars(field_charset(),
+                                                   a_ptr, field_len,
+                                                   b_ptr, field_len,
+                                                   prefix_char_len,
+                                                   0);
+}
+
+
 void Field_string::sort_string(uchar *to,uint length)
 {
 #ifdef DBUG_ASSERT_EXISTS
diff --git a/sql/field.h b/sql/field.h
index 4a95a6e05568c..aeb2ae0d20a80 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -4038,6 +4038,8 @@ class Field_string final :public Field_longstr {
   String *val_str(String *, String *) override;
   my_decimal *val_decimal(my_decimal *) override;
   int cmp(const uchar *,const uchar *) const override;
+  int cmp_prefix(const uchar *a, const uchar *b, size_t prefix_char_len) const
+    override;
   void sort_string(uchar *buff,uint length) override;
   void update_data_type_statistics(Data_type_statistics *st) const override
   {
diff --git a/sql/key.cc b/sql/key.cc
index d801bcc982b8f..2fa7d7066a4b5 100644
--- a/sql/key.cc
+++ b/sql/key.cc
@@ -605,7 +605,7 @@ int key_rec_cmp(void *key_p, uchar *first_rec, uchar *second_rec)
       }
       /*
         No null values in the fields
-        We use the virtual method cmp_max with a max length parameter.
+        We use the virtual method cmp_prefix with a max length parameter.
         For most field types this translates into a cmp without
         max length. The exceptions are the BLOB and VARCHAR field types
         that take the max length into account.
diff --git a/sql/table.cc b/sql/table.cc
index a5e33052d3f5b..f3d186f4d9db8 100644
--- a/sql/table.cc
+++ b/sql/table.cc
@@ -1272,12 +1272,11 @@ bool parse_vcol_defs(THD *thd, MEM_ROOT *mem_root, TABLE *table,
         if (keypart->key_part_flag & HA_PART_KEY_SEG)
         {
           int length= keypart->length/keypart->field->charset()->mbmaxlen;
+          Field *kpf= table->field[keypart->field->field_index];
           list_item= new (mem_root) Item_func_left(thd,
-                       new (mem_root) Item_field(thd, keypart->field),
+                       new (mem_root) Item_field(thd, kpf),
                        new (mem_root) Item_int(thd, length));
           list_item->fix_fields(thd, NULL);
-          keypart->field->vcol_info=
-            table->field[keypart->field->field_index]->vcol_info;
         }
         else
           list_item= new (mem_root) Item_field(thd, keypart->field);