diff --git a/ChangeLog.md b/ChangeLog.md
--- a/ChangeLog.md
+++ b/ChangeLog.md
@@ -1,3 +1,7 @@
+## 0.4.2.0
+
+* Handle fractional seconds in parameter substitution (without affecting cases where only whole seconds are used).  https://github.com/paul-rouse/mysql-simple/pull/40
+
 ## 0.4.1.0
 
 * Add missing tuple instances of QueryResults (https://github.com/paul-rouse/mysql-simple/issues/9)
diff --git a/Database/MySQL/Simple/Param.hs b/Database/MySQL/Simple/Param.hs
--- a/Database/MySQL/Simple/Param.hs
+++ b/Database/MySQL/Simple/Param.hs
@@ -190,7 +190,7 @@
     {-# INLINE render #-}
 
 instance Param UTCTime where
-    render = Plain . Utf8.fromString . formatTime defaultTimeLocale "'%F %T'"
+    render = Plain . Utf8.fromString . formatTime defaultTimeLocale "'%F %T%Q'"
     {-# INLINE render #-}
 
 instance Param Day where
diff --git a/mysql-simple.cabal b/mysql-simple.cabal
--- a/mysql-simple.cabal
+++ b/mysql-simple.cabal
@@ -1,5 +1,5 @@
 name:           mysql-simple
-version:        0.4.1.0
+version:        0.4.2.0
 homepage:       https://github.com/paul-rouse/mysql-simple
 bug-reports:    https://github.com/paul-rouse/mysql-simple/issues
 synopsis:       A mid-level MySQL client library.