diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,15 @@
+## 0.2.1
+
+* Work around incorrect test for header-file definition of MYSQL_TYPE_JSON (#45 and 51464fa)
+
+## 0.2.0.1
+
+* Make connection finalizer thread safe (#28).
+
+## 0.2
+
+* Remove obsolete `fieldDefault` from `data Field` (#41).
+
 ## 0.1.7.3
 
 * Fix error on certain systems introduced by the change in (#40): some implementations of `mysql_config` do not recognise `--libs-sys`, yet return a zero status for attempts to use it.
diff --git a/Database/MySQL/Base.hs b/Database/MySQL/Base.hs
--- a/Database/MySQL/Base.hs
+++ b/Database/MySQL/Base.hs
@@ -85,6 +85,7 @@
     ) where
 
 import Control.Applicative ((<$>), (<*>))
+import Control.Concurrent (rtsSupportsBoundThreads, runInBoundThread)
 import Control.Exception (Exception, throw)
 import Control.Monad (forM_, unless, when)
 import Data.ByteString.Char8 ()
@@ -300,7 +301,11 @@
         cleanupConnResult res
         wasClosed <- atomicModifyIORef closed $ \prev -> (True, prev)
         unless wasClosed $ mysql_close ptr
-  fp <- newForeignPtr ptr realClose
+  -- In general, the user of this library is responsible for dealing with thread
+  -- safety. However, the programmer has no control over the OS thread
+  -- finalizers are run from so we use 'runInBoundThread' and 'initThread' here.
+  let myRunInBoundThread = if rtsSupportsBoundThreads then runInBoundThread else id
+  fp <- newForeignPtr ptr (myRunInBoundThread $ initThread >> realClose)
   return Connection {
                connFP = fp
              , connClose = realClose
diff --git a/Database/MySQL/Base/Types.hsc b/Database/MySQL/Base/Types.hsc
--- a/Database/MySQL/Base/Types.hsc
+++ b/Database/MySQL/Base/Types.hsc
@@ -69,6 +69,15 @@
 type MYSQL_ROW_OFFSET = Ptr MYSQL_ROWS
 type MyBool = CChar
 
+-- "mysql.h" defines the `MYSQL_TYPE_...` symbols as values of an enumeration,
+-- not as preprocessor symbols.  Therefore we can't test for the presence of
+-- `MYSQL_TYPE_JSON` using `#ifdef` or `#if defined()`, yet it is not available
+-- in all versions of MySQL and MariaDB.  Although this is very unsatisfactory,
+-- we have little alternative but to define it here.
+--
+mysql_type_json :: Int
+mysql_type_json = 245
+
 -- | Column types supported by MySQL.
 data Type = Decimal
           | Tiny
@@ -132,9 +141,7 @@
       , ((#const MYSQL_TYPE_VAR_STRING), VarString)
       , ((#const MYSQL_TYPE_STRING), String)
       , ((#const MYSQL_TYPE_GEOMETRY), Geometry)
-#if defined(MYSQL_TYPE_JSON)
-      , ((#const MYSQL_TYPE_JSON), Json)
-#endif
+      , (mysql_type_json, Json)
       ]
 
 -- | A description of a field (column) of a table.
@@ -145,7 +152,6 @@
     , fieldOrigTable :: ByteString -- ^ Original table name, if table was an alias.
     , fieldDB :: ByteString        -- ^ Database for table.
     , fieldCatalog :: ByteString   -- ^ Catalog for table.
-    , fieldDefault :: Maybe ByteString   -- ^ Default value.
     , fieldLength :: Word          -- ^ Width of column (create length).
     , fieldMaxLength :: Word    -- ^ Maximum width for selected set.
     , fieldFlags :: FieldFlags        -- ^ Div flags.
@@ -216,9 +222,6 @@
    <*> peekS ((#peek MYSQL_FIELD, org_table)) ((#peek MYSQL_FIELD, org_table_length))
    <*> peekS ((#peek MYSQL_FIELD, db)) ((#peek MYSQL_FIELD, db_length))
    <*> peekS ((#peek MYSQL_FIELD, catalog)) ((#peek MYSQL_FIELD, catalog_length))
-   <*> (if flags `hasAllFlags` flagNoDefaultValue
-       then pure Nothing
-       else Just <$> peekS ((#peek MYSQL_FIELD, def)) ((#peek MYSQL_FIELD, def_length)))
    <*> (uint <$> (#peek MYSQL_FIELD, length) ptr)
    <*> (uint <$> (#peek MYSQL_FIELD, max_length) ptr)
    <*> pure flags
diff --git a/mysql.cabal b/mysql.cabal
--- a/mysql.cabal
+++ b/mysql.cabal
@@ -1,5 +1,5 @@
 name:           mysql
-version:        0.1.7.3
+version:        0.2.1
 homepage:       https://github.com/paul-rouse/mysql
 bug-reports:    https://github.com/paul-rouse/mysql/issues
 synopsis:       A low-level MySQL client library.