diff --git a/mysql-test/suite/binlog/r/binlog_max_extension.result b/mysql-test/suite/binlog/r/binlog_max_extension.result
new file mode 100644
index 00000000000..af341db4536
--- /dev/null
+++ b/mysql-test/suite/binlog/r/binlog_max_extension.result
@@ -0,0 +1,8 @@
+call mtr.add_suppression("Next log extension: 2147483647. Remaining log filename extensions: 0.");
+call mtr.add_suppression("Log filename extension number exhausted:");
+call mtr.add_suppression("Can't generate a unique log-filename");
+RESET MASTER;
+FLUSH LOGS;
+Warnings:
+Warning	1098	Can't generate a unique log-filename master-bin.(1-999)
+
diff --git a/mysql-test/suite/binlog/t/binlog_max_extension.test b/mysql-test/suite/binlog/t/binlog_max_extension.test
new file mode 100644
index 00000000000..9f52d195e21
--- /dev/null
+++ b/mysql-test/suite/binlog/t/binlog_max_extension.test
@@ -0,0 +1,92 @@
+#  BUG#40611: MySQL cannot make a binary log after sequential number beyond 
+#             unsigned long.
+# 
+#  Problem statement
+#  =================
+#
+#    Extension for log file names might be created with negative 
+#    numbers (when counter used would wrap around), causing server 
+#    failure when incrementing -00001 (reaching number 000000 
+#    extension).
+#
+#  Test
+#  ====
+#    This tests aims at testing the a patch that removes negatives 
+#    numbers from log name extensions and checks that the server 
+#    reports gracefully that the limit has been reached.
+#
+#    It instruments index file to point to a log file close to
+#    the new maximum and calls flush logs to get warning.
+#
+
+call mtr.add_suppression("Next log extension: 2147483647. Remaining log filename extensions: 0.");
+call mtr.add_suppression("Log filename extension number exhausted:");
+call mtr.add_suppression("Can't generate a unique log-filename");
+
+
+-- source include/have_log_bin.inc
+RESET MASTER;
+
+-- let $MYSQLD_DATADIR= `select @@datadir`
+
+###############################################
+# check hitting maximum file name extension:
+###############################################
+
+##########
+# Prepare
+##########
+
+# 1. Stop master server
+-- write_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+wait
+EOF
+-- shutdown_server 10
+-- source include/wait_until_disconnected.inc
+
+# 2. Prepare log and index file
+-- copy_file $MYSQLD_DATADIR/master-bin.index $MYSQLD_DATADIR/master-bin.index.orig
+-- copy_file $MYSQLD_DATADIR/master-bin.000001 $MYSQLD_DATADIR/master-bin.2147483646
+-- append_file $MYSQLD_DATADIR/master-bin.index
+master-bin.2147483646
+EOF
+
+# 3. Restart the server
+-- append_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+restart
+EOF
+-- enable_reconnect
+-- source include/wait_until_connected_again.inc
+
+###########
+# Assertion
+###########
+
+# assertion: should throw warning
+FLUSH LOGS;
+
+##############
+# Clean up
+##############
+
+# 1. Stop the server
+-- write_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+wait
+EOF
+-- shutdown_server 10
+-- source include/wait_until_disconnected.inc
+
+# 2. Undo changes to index and log files
+-- remove_file $MYSQLD_DATADIR/master-bin.index
+-- copy_file $MYSQLD_DATADIR/master-bin.index.orig $MYSQLD_DATADIR/master-bin.index
+-- remove_file $MYSQLD_DATADIR/master-bin.index.orig
+
+-- remove_file $MYSQLD_DATADIR/master-bin.2147483646
+-- remove_file $MYSQLD_DATADIR/master-bin.2147483647
+
+# 3. Restart the server
+-- append_file $MYSQLTEST_VARDIR/tmp/mysqld.1.expect
+restart
+EOF
+-- enable_reconnect
+-- source include/wait_until_connected_again.inc
diff --git a/sql/log.cc b/sql/log.cc
index 5c25d30bad0..19b26fcf5ab 100644
--- a/sql/log.cc
+++ b/sql/log.cc
@@ -53,7 +53,7 @@ MYSQL_BIN_LOG mysql_bin_log;
 ulong sync_binlog_counter= 0;
 
 static bool test_if_number(const char *str,
-			   long *res, bool allow_wildcards);
+			   ulong *res, bool allow_wildcards);
 static int binlog_init(void *p);
 static int binlog_close_connection(handlerton *hton, THD *thd);
 static int binlog_savepoint_set(handlerton *hton, THD *thd, void *sv);
@@ -1835,22 +1835,27 @@ static void setup_windows_event_source()
 /**
   Find a unique filename for 'filename.#'.
 
-  Set '#' to a number as low as possible.
+  Set '#' to the number next to the maximum found in the most
+  recent log file extension.
+
+  This function will return nonzero if: (i) the generated name
+  exceeds FN_REFLEN; (ii) if the number of extensions is exhausted;
+  or (iii) some other error happened while examining the filesystem.
 
   @return
-    nonzero if not possible to get unique filename
+    nonzero if not possible to get unique filename.
 */
 
 static int find_uniq_filename(char *name)
 {
-  long                  number;
   uint                  i;
-  char                  buff[FN_REFLEN];
+  char                  buff[FN_REFLEN], ext_buf[FN_REFLEN];
   struct st_my_dir     *dir_info;
   reg1 struct fileinfo *file_info;
-  ulong                 max_found=0;
+  ulong                 max_found= 0, next= 0, number= 0;
   size_t		buf_length, length;
   char			*start, *end;
+  int                   error= 0;
   DBUG_ENTER("find_uniq_filename");
 
   length= dirname_part(buff, name, &buf_length);
@@ -1858,15 +1863,15 @@ static int find_uniq_filename(char *name)
   end=    strend(start);
 
   *end='.';
-  length= (size_t) (end-start+1);
+  length= (size_t) (end - start + 1);
 
-  if (!(dir_info = my_dir(buff,MYF(MY_DONT_SORT))))
+  if (!(dir_info= my_dir(buff,MYF(MY_DONT_SORT))))
   {						// This shouldn't happen
     strmov(end,".1");				// use name+1
-    DBUG_RETURN(0);
+    DBUG_RETURN(1);
   }
   file_info= dir_info->dir_entry;
-  for (i=dir_info->number_off_files ; i-- ; file_info++)
+  for (i= dir_info->number_off_files ; i-- ; file_info++)
   {
     if (bcmp((uchar*) file_info->name, (uchar*) start, length) == 0 &&
 	test_if_number(file_info->name+length, &number,0))
@@ -1876,9 +1881,44 @@ static int find_uniq_filename(char *name)
   }
   my_dirend(dir_info);
 
+  /* check if reached the maximum possible extension number */
+  if ((max_found == MAX_LOG_UNIQUE_FN_EXT))
+  {
+    sql_print_error("Log filename extension number exhausted: %06lu. \
+Please fix this by archiving old logs and \
+updating the index files.", max_found);
+    error= 1;
+    goto end;
+  }
+
+  next= max_found + 1;
+  sprintf(ext_buf, "%06lu", next);
   *end++='.';
-  sprintf(end,"%06ld",max_found+1);
-  DBUG_RETURN(0);
+
+  /* 
+    Check if the generated extension size + the file name exceeds the
+    buffer size used. If one did not check this, then the filename might be
+    truncated, resulting in error.
+   */
+  if (((strlen(ext_buf) + (end - name)) >= FN_REFLEN))
+  {
+    sql_print_error("Log filename too large: %s%s (%d). \
+Please fix this by archiving old logs and updating the \
+index files.", name, ext_buf, (strlen(ext_buf) + (end - name)));
+    error= 1;
+    goto end;
+  }
+
+  sprintf(end, "%06lu", next);
+
+  /* print warning if reaching the end of available extensions. */
+  if ((next > (MAX_LOG_UNIQUE_FN_EXT - LOG_WARN_UNIQUE_FN_EXT_LEFT)))
+    sql_print_warning("Next log extension: %lu. \
+Remaining log filename extensions: %lu. \
+Please consider archiving some logs.", next, (MAX_LOG_UNIQUE_FN_EXT - next));
+
+end:
+  DBUG_RETURN(error);
 }
 
 
@@ -2077,6 +2117,13 @@ int MYSQL_LOG::generate_new_name(char *new_name, const char *log_name)
     {
       if (find_uniq_filename(new_name))
       {
+        /* 
+          This should be treated as error once propagation of error further
+          up in the stack gets proper handling.
+        */
+        push_warning_printf(current_thd, MYSQL_ERROR::WARN_LEVEL_WARN, 
+                            ER_NO_UNIQUE_LOGFILE, ER(ER_NO_UNIQUE_LOGFILE),
+                            log_name);
 	sql_print_error(ER(ER_NO_UNIQUE_LOGFILE), log_name);
 	return 1;
       }
@@ -4739,11 +4786,11 @@ void MYSQL_BIN_LOG::set_max_size(ulong max_size_arg)
   @retval
     1	String is a number
   @retval
-    0	Error
+    0	String is not a number
 */
 
 static bool test_if_number(register const char *str,
-			   long *res, bool allow_wildcards)
+			   ulong *res, bool allow_wildcards)
 {
   reg2 int flag;
   const char *start;
diff --git a/sql/log.h b/sql/log.h
index d306d6f7182..3c2ccc521cc 100644
--- a/sql/log.h
+++ b/sql/log.h
@@ -121,6 +121,19 @@ extern TC_LOG_DUMMY tc_log_dummy;
 #define LOG_CLOSE_TO_BE_OPENED	2
 #define LOG_CLOSE_STOP_EVENT	4
 
+/* 
+  Maximum unique log filename extension.
+  Note: setting to 0x7FFFFFFF due to atol windows 
+        overflow/truncate.
+ */
+#define MAX_LOG_UNIQUE_FN_EXT 0x7FFFFFFF
+
+/* 
+   Number of warnings that will be printed to error log
+   before extension number is exhausted.
+*/
+#define LOG_WARN_UNIQUE_FN_EXT_LEFT 1000
+
 class Relay_log_info;
 
 typedef struct st_log_info