diff --git a/google-search.cabal b/google-search.cabal
--- a/google-search.cabal
+++ b/google-search.cabal
@@ -1,5 +1,5 @@
 name:           google-search
-version:        0.1.0.1
+version:        0.2.0.0
 synopsis:       EDSL for Google and GMail search expressions
 description:
   Construct well-typed search expressions for use in various Google services.
@@ -13,22 +13,31 @@
 build-type:     Simple
 cabal-version:  >= 1.8
 stability:      experimental
+tested-with:
+    GHC == 7.4.2, GHC == 7.6.3, GHC == 7.8.4,
+    GHC == 7.10.2, GHC == 7.10.3
 
 source-repository head
-  type:     git
-  location: http://github.com/liyang/google-search
+    type:     git
+    location: http://github.com/liyang/google-search
 
+flag old-time
+    description: time < 1.5
+    default: False
+
 library
-  hs-source-dirs: src
-  exposed-modules:
-    Language.Google.Search.Simple
-    Language.Google.Search.Mail
-  build-depends:
-    base >= 4.5 && <= 9000,
-    free >= 2.1,
-    nats >= 0.1,
-    old-locale >= 1.0,
-    text >= 0.11,
-    time >= 1.4
-  ghc-options: -Wall
+    hs-source-dirs: src
+    ghc-options: -Wall
+    exposed-modules:
+        Language.Google.Search.Simple
+        Language.Google.Search.Mail
+    build-depends:
+        base >= 4.5 && <= 9000,
+        free >= 2.1,
+        nats >= 0.1,
+        text >= 0.11
+    if flag(old-time)
+        build-depends: old-locale >= 1.0, time >= 1.4 && < 1.5
+    else
+        build-depends: time >= 1.5
 
diff --git a/src/Language/Google/Search/Mail.hs b/src/Language/Google/Search/Mail.hs
--- a/src/Language/Google/Search/Mail.hs
+++ b/src/Language/Google/Search/Mail.hs
@@ -1,3 +1,4 @@
+{-# LANGUAGE CPP #-}
 {-# LANGUAGE OverloadedStrings #-}
 
 -- | <https://support.google.com/mail/answer/7190>
@@ -14,7 +15,12 @@
 import Data.Time.Calendar (Day)
 import Data.Time.Format (formatTime)
 import Numeric.Natural
+
+#if MIN_VERSION_time(1,5,0)
+import Data.Time.Format (defaultTimeLocale)
+#else
 import System.Locale (defaultTimeLocale)
+#endif
 
 import Language.Google.Search.Simple
 
@@ -71,7 +77,7 @@
     | From Simple
     | To Simple
     | Subject Simple
-    | Label Text
+    | Label (BooleanM Text)
     | Has Feature
     | List Simple
     | Filename Simple
@@ -103,7 +109,7 @@
         From s          -> "from:"          <>? s
         To s            -> "to:"            <>? s
         Subject s       -> "subject:"       <>? s
-        Label t         -> "label:"         <>! B.fromText t
+        Label s         -> "label:"         <>? s
         Has ft          -> "has:"           <>! case ft of
             Attachment      -> "attachment"
             BlueInfo        -> "blue-info"