diff --git a/src/utils/transforms.lisp b/src/utils/transforms.lisp
index dff12d1..7dfa473 100644
--- a/src/utils/transforms.lisp
+++ b/src/utils/transforms.lisp
@@ -145,7 +145,13 @@
   "When using MySQL, strange things will happen, like encoding booleans into
    bit(1). Of course PostgreSQL wants 'f' and 't'."
   (when (and bit-vector (= 1 (length bit-vector)))
-    (if (= 0 (aref bit-vector 0)) "f" "t")))
+    (let ((bit (aref bit-vector 0)))
+      ;; we might have either a char or a number here, see issue #684.
+      ;; current guess when writing the code is that it depends on MySQL
+      ;; version, but this has not been checked.
+      (etypecase bit
+        (fixnum    (if (= 0 bit) "f" "t"))
+        (character (if (= 0 (char-code bit)) "f" "t"))))))
 
 (defun int-to-ip (int)
   "Transform an IP as integer into its dotted notation, optimised code from
diff --git a/test/mysql/my.sql b/test/mysql/my.sql
index ab12fc3..44234f1 100644
--- a/test/mysql/my.sql
+++ b/test/mysql/my.sql
@@ -89,6 +89,17 @@ CREATE TABLE pgloader_test_unsigned
 );
 INSERT INTO pgloader_test_unsigned(id) VALUES (65535);
 
+/*
+ * https://github.com/dimitri/pgloader/issues/684
+ */
+create table bits
+ (
+  id   integer not null AUTO_INCREMENT primary key,
+  bool bit(1)
+ );
+
+insert into bits(bool) values(0b00), (0b01);
+
 CREATE TABLE `fcm_batches` (
   `id` int(10) unsigned NOT NULL AUTO_INCREMENT,
   `raw_payload` mediumtext COLLATE utf8_unicode_ci,