diff --git a/mysql-test/main/func_str.result b/mysql-test/main/func_str.result
index c071b92318a..e5a21af03a3 100644
--- a/mysql-test/main/func_str.result
+++ b/mysql-test/main/func_str.result
@@ -5311,5 +5311,13 @@ NULL
 DROP TABLE t1;
 DROP VIEW v1;
 #
+# MDEV-28387 UBSAN: runtime error: negation of -9223372036854775808 cannot be represented in type 'long long int'; cast to an unsigned type to negate this value to itself in my_strtoll10 on SELECT
+#
+SET @a='-9223372036854775808';
+CREATE TABLE t (c1 INT,c2 CHAR);
+SELECT SUBSTR(0,@a) FROM t;
+SUBSTR(0,@a)
+DROP TABLE t;
+#
 # End of 10.5 tests
 #
diff --git a/mysql-test/main/func_str.test b/mysql-test/main/func_str.test
index 69161349720..49b5546abb8 100644
--- a/mysql-test/main/func_str.test
+++ b/mysql-test/main/func_str.test
@@ -2348,6 +2348,15 @@ DROP TABLE t1;
 DROP VIEW v1;
 
 
+--echo #
+--echo # MDEV-28387 UBSAN: runtime error: negation of -9223372036854775808 cannot be represented in type 'long long int'; cast to an unsigned type to negate this value to itself in my_strtoll10 on SELECT
+--echo #
+
+SET @a='-9223372036854775808';  # Quite specific value; considerably varying it will not work
+CREATE TABLE t (c1 INT,c2 CHAR);
+SELECT SUBSTR(0,@a) FROM t;
+DROP TABLE t;
+
 --echo #
 --echo # End of 10.5 tests
 --echo #
diff --git a/strings/my_strtoll10.c b/strings/my_strtoll10.c
index 183829d7074..8144be7a1da 100644
--- a/strings/my_strtoll10.c
+++ b/strings/my_strtoll10.c
@@ -241,7 +241,7 @@ end4:
   *endptr= (char*) s;
   if (negative)
   {
-   if (li > MAX_NEGATIVE_NUMBER)
+   if (li >= MAX_NEGATIVE_NUMBER)
      goto overflow;
    return -((longlong) li);
   }