diff --git a/mysql-test/main/func_str.result b/mysql-test/main/func_str.result
index 22cf0a5cc56..eb00837eaaf 100644
--- a/mysql-test/main/func_str.result
+++ b/mysql-test/main/func_str.result
@@ -5068,5 +5068,21 @@ NULL
 
 DROP TABLE t1;
 #
+# MDEV-20292 REPEAT(x,-1) returns a wrong data type
+#
+CREATE OR REPLACE TABLE t1 (i BIGINT);
+INSERT INTO t1 VALUES (42);
+CREATE OR REPLACE TABLE t2 AS SELECT
+REPEAT(i,0) AS c0,
+REPEAT(i,-1) AS c1
+FROM t1;
+SHOW CREATE TABLE t2;
+Table	Create Table
+t2	CREATE TABLE `t2` (
+  `c0` char(0) CHARACTER SET utf8 DEFAULT NULL,
+  `c1` char(0) CHARACTER SET utf8 DEFAULT NULL
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+DROP TABLE t1, t2;
+#
 # End of 10.3 tests
 #
diff --git a/mysql-test/main/func_str.test b/mysql-test/main/func_str.test
index c122516d756..135d00bcd8c 100644
--- a/mysql-test/main/func_str.test
+++ b/mysql-test/main/func_str.test
@@ -2028,6 +2028,19 @@ SELECT LPAD( c, 0, '?' ) FROM t1;
 SELECT RPAD( c, 0, '?' ) FROM t1;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-20292 REPEAT(x,-1) returns a wrong data type
+--echo #
+
+CREATE OR REPLACE TABLE t1 (i BIGINT);
+INSERT INTO t1 VALUES (42);
+CREATE OR REPLACE TABLE t2 AS SELECT
+  REPEAT(i,0) AS c0,
+  REPEAT(i,-1) AS c1
+FROM t1;
+SHOW CREATE TABLE t2;
+DROP TABLE t1, t2;
+
 
 --echo #
 --echo # End of 10.3 tests
diff --git a/sql/item_strfunc.cc b/sql/item_strfunc.cc
index 3d2b3ef4814..65acc071237 100644
--- a/sql/item_strfunc.cc
+++ b/sql/item_strfunc.cc
@@ -2967,20 +2967,20 @@ bool Item_func_repeat::fix_length_and_dec()
   if (agg_arg_charsets_for_string_result(collation, args, 1))
     return TRUE;
   DBUG_ASSERT(collation.collation != NULL);
-  if (args[1]->const_item())
+  if (args[1]->const_item() && !args[1]->is_expensive())
   {
-    /* must be longlong to avoid truncation */
-    longlong count= args[1]->val_int();
-
-    /* Assumes that the maximum length of a String is < INT_MAX32. */
-    /* Set here so that rest of code sees out-of-bound value as such. */
-    if (args[1]->null_value)
-      count= 0;
-    else if (count > INT_MAX32)
-      count= INT_MAX32;
-
-    ulonglong char_length= (ulonglong) args[0]->max_char_length() * count;
-    fix_char_length_ulonglong(char_length);
+    Longlong_hybrid nr= args[1]->to_longlong_hybrid();
+    if (args[1]->null_value || nr.neg())
+      fix_char_length(0);
+    else
+    {
+      /* Assumes that the maximum length of a String is < INT_MAX32. */
+      longlong count= nr.value();
+      if (count > INT_MAX32)
+        count= INT_MAX32;
+      ulonglong char_length= (ulonglong) args[0]->max_char_length() * count;
+      fix_char_length_ulonglong(char_length);
+    }
   }
   else
   {