diff --git a/CHANGELOG b/CHANGELOG
--- a/CHANGELOG
+++ b/CHANGELOG
@@ -1,3 +1,9 @@
+- 0.2.4.0 (2017-09-27)
+    * Add `unsafeMapMonotonic`
+    * Lower build depends version for hashable
+    * Move repo to `jaspervdj/psqueues` to enable travis
+    * Lower build depends version for hashable
+
 - 0.2.3.0
     * Add an `atMostView` function to all PSQ flavours
     * Bump HUnit dependency to 1.6
diff --git a/psqueues.cabal b/psqueues.cabal
--- a/psqueues.cabal
+++ b/psqueues.cabal
@@ -1,9 +1,9 @@
 Name:          psqueues
-Version:       0.2.3.0
+Version:       0.2.4.0
 License:       BSD3
 License-file:  LICENSE
 Maintainer:    Jasper Van der Jeugt <jaspervdj@gmail.com>
-Bug-reports:   https://github.com/bttr/psqueues/issues
+Bug-reports:   https://github.com/jaspervdj/psqueues/issues
 Synopsis:      Pure priority search queues
 Category:      Data Structures
 Build-type:    Simple
@@ -57,16 +57,16 @@
 
 Source-repository head
     type:     git
-    location: http://github.com/bttr/psqueues.git
+    location: http://github.com/jaspervdj/psqueues.git
 
 Library
     Ghc-options:    -O2 -Wall
     Hs-source-dirs: src
 
     Build-depends:
-          base     >= 4.2   && < 5
-        , deepseq  >= 1.2   && < 1.5
-        , hashable >= 1.2.1 && < 1.3
+          base     >= 4.2     && < 5
+        , deepseq  >= 1.2     && < 1.5
+        , hashable >= 1.1.2.3 && < 1.3
 
     if impl(ghc>=6.10)
         Build-depends: ghc-prim
diff --git a/src/Data/HashPSQ.hs b/src/Data/HashPSQ.hs
--- a/src/Data/HashPSQ.hs
+++ b/src/Data/HashPSQ.hs
@@ -41,6 +41,7 @@
 
       -- * Traversal
     , map
+    , unsafeMapMonotonic
     , fold'
 
       -- * Validity check
diff --git a/src/Data/HashPSQ/Internal.hs b/src/Data/HashPSQ/Internal.hs
--- a/src/Data/HashPSQ/Internal.hs
+++ b/src/Data/HashPSQ/Internal.hs
@@ -43,6 +43,7 @@
 
       -- * Traversal
     , map
+    , unsafeMapMonotonic
     , fold'
 
       -- * Unsafe operations
@@ -389,6 +390,23 @@
 map f (HashPSQ ipsq) = HashPSQ (IntPSQ.map (\_ p v -> mapBucket p v) ipsq)
   where
     mapBucket p (B k v opsq) = B k (f k p v) (OrdPSQ.map f opsq)
+
+-- | /O(n)/ Maps a function over the values and priorities of the queue.
+-- The function @f@ must be monotonic with respect to the priorities. I.e. if
+-- @x < y@, then @fst (f k x v) < fst (f k y v)@.
+-- /The precondition is not checked./ If @f@ is not monotonic, then the result
+-- will be invalid.
+{-# INLINABLE unsafeMapMonotonic #-}
+unsafeMapMonotonic
+    :: (k -> p -> v -> (q, w))
+    -> HashPSQ k p v
+    -> HashPSQ k q w
+unsafeMapMonotonic f (HashPSQ ipsq) =
+  HashPSQ (IntPSQ.unsafeMapMonotonic (\_ p v -> mapBucket p v) ipsq)
+  where
+    mapBucket p (B k v opsq) =
+        let (p', v') = f k p v
+        in  (p', B k v' (OrdPSQ.unsafeMapMonotonic f opsq))
 
 -- | /O(n)/ Strict fold over every key, priority and value in the queue. The order
 -- in which the fold is performed is not specified.
diff --git a/src/Data/IntPSQ.hs b/src/Data/IntPSQ.hs
--- a/src/Data/IntPSQ.hs
+++ b/src/Data/IntPSQ.hs
@@ -44,6 +44,7 @@
 
       -- * Traversal
     , map
+    , unsafeMapMonotonic
     , fold'
 
       -- * Validity check
diff --git a/src/Data/IntPSQ/Internal.hs b/src/Data/IntPSQ/Internal.hs
--- a/src/Data/IntPSQ/Internal.hs
+++ b/src/Data/IntPSQ/Internal.hs
@@ -44,6 +44,7 @@
 
       -- * Traversal
     , map
+    , unsafeMapMonotonic
     , fold'
 
       -- * Unsafe manipulation
@@ -463,6 +464,23 @@
         Nil             -> Nil
         Tip k p x       -> Tip k p (f k p x)
         Bin k p x m l r -> Bin k p (f k p x) m (go l) (go r)
+
+-- | /O(n)/ Maps a function over the values and priorities of the queue.
+-- The function @f@ must be monotonic with respect to the priorities. I.e. if
+-- @x < y@, then @fst (f k x v) < fst (f k y v)@.
+-- /The precondition is not checked./ If @f@ is not monotonic, then the result
+-- will be invalid.
+{-# INLINABLE unsafeMapMonotonic #-}
+unsafeMapMonotonic :: (Key -> p -> v -> (q, w)) -> IntPSQ p v -> IntPSQ q w
+unsafeMapMonotonic f = go
+  where
+    go t = case t of
+        Nil             -> Nil
+        Tip k p x       -> let (p', x') = f k p x
+                           in  Tip k p' x'
+
+        Bin k p x m l r -> let (p', x') = f k p x
+                           in  Bin k p' x' m (go l) (go r)
 
 -- | /O(n)/ Strict fold over every key, priority and value in the queue. The order
 -- in which the fold is performed is not specified.
diff --git a/src/Data/OrdPSQ.hs b/src/Data/OrdPSQ.hs
--- a/src/Data/OrdPSQ.hs
+++ b/src/Data/OrdPSQ.hs
@@ -51,6 +51,7 @@
 
       -- * Traversals
     , map
+    , unsafeMapMonotonic
     , fold'
 
       -- * Validity check
diff --git a/src/Data/OrdPSQ/Internal.hs b/src/Data/OrdPSQ/Internal.hs
--- a/src/Data/OrdPSQ/Internal.hs
+++ b/src/Data/OrdPSQ/Internal.hs
@@ -44,6 +44,7 @@
 
       -- * Traversals
     , map
+    , unsafeMapMonotonic
     , fold'
 
       -- * Tournament view
@@ -393,6 +394,31 @@
     goLTree (LLoser s e l k r) = LLoser s (goElem e) (goLTree l) k (goLTree r)
     goLTree (RLoser s e l k r) = RLoser s (goElem e) (goLTree l) k (goLTree r)
 
+-- | /O(n)/ Maps a function over the values and priorities of the queue.
+-- The function @f@ must be monotonic with respect to the priorities. I.e. if
+-- @x < y@, then @fst (f k x v) < fst (f k y v)@.
+-- /The precondition is not checked./ If @f@ is not monotonic, then the result
+-- will be invalid.
+{-# INLINABLE unsafeMapMonotonic #-}
+unsafeMapMonotonic
+    :: forall k p q v w.
+       (k -> p -> v -> (q, w))
+    -> OrdPSQ k p v
+    -> OrdPSQ k q w
+unsafeMapMonotonic f = goPSQ
+  where
+    goPSQ :: OrdPSQ k p v -> OrdPSQ k q w
+    goPSQ Void           = Void
+    goPSQ (Winner e l k) = Winner (goElem e) (goLTree l) k
+
+    goElem :: Elem k p v -> Elem k q w
+    goElem (E k p x) = let (p', x') = f k p x
+                       in E k p' x'
+
+    goLTree :: LTree k p v -> LTree k q w
+    goLTree Start              = Start
+    goLTree (LLoser s e l k r) = LLoser s (goElem e) (goLTree l) k (goLTree r)
+    goLTree (RLoser s e l k r) = RLoser s (goElem e) (goLTree l) k (goLTree r)
 
 -- | /O(n)/ Strict fold over every key, priority and value in the queue. The order
 -- in which the fold is performed is not specified.
diff --git a/tests/Data/PSQ/Class.hs b/tests/Data/PSQ/Class.hs
--- a/tests/Data/PSQ/Class.hs
+++ b/tests/Data/PSQ/Class.hs
@@ -73,6 +73,8 @@
 
     -- Traversals
     map :: Ord p => (Key psq -> p -> v -> w) -> psq p v -> psq p w
+    unsafeMapMonotonic
+        :: (Ord p, Ord q) => (Key psq -> p -> v -> (q, w)) -> psq p v -> psq q w
     fold'
         :: Ord p => (Key psq -> p -> v -> a -> a) -> a -> psq p v -> a
 
@@ -83,77 +85,80 @@
 instance PSQ IntPSQ.IntPSQ where
     type Key IntPSQ.IntPSQ = Int
 
-    null       = IntPSQ.null
-    size       = IntPSQ.size
-    member     = IntPSQ.member
-    lookup     = IntPSQ.lookup
-    findMin    = IntPSQ.findMin
-    empty      = IntPSQ.empty
-    singleton  = IntPSQ.singleton
-    insert     = IntPSQ.insert
-    delete     = IntPSQ.delete
-    deleteMin  = IntPSQ.deleteMin
-    alter      = IntPSQ.alter
-    alterMin   = IntPSQ.alterMin
-    fromList   = IntPSQ.fromList
-    toList     = IntPSQ.toList
-    keys       = IntPSQ.keys
-    insertView = IntPSQ.insertView
-    deleteView = IntPSQ.deleteView
-    minView    = IntPSQ.minView
-    atMostView = IntPSQ.atMostView
-    map        = IntPSQ.map
-    fold'      = IntPSQ.fold'
-    valid      = IntPSQ.valid
+    null               = IntPSQ.null
+    size               = IntPSQ.size
+    member             = IntPSQ.member
+    lookup             = IntPSQ.lookup
+    findMin            = IntPSQ.findMin
+    empty              = IntPSQ.empty
+    singleton          = IntPSQ.singleton
+    insert             = IntPSQ.insert
+    delete             = IntPSQ.delete
+    deleteMin          = IntPSQ.deleteMin
+    alter              = IntPSQ.alter
+    alterMin           = IntPSQ.alterMin
+    fromList           = IntPSQ.fromList
+    toList             = IntPSQ.toList
+    keys               = IntPSQ.keys
+    insertView         = IntPSQ.insertView
+    deleteView         = IntPSQ.deleteView
+    minView            = IntPSQ.minView
+    atMostView         = IntPSQ.atMostView
+    map                = IntPSQ.map
+    unsafeMapMonotonic = IntPSQ.unsafeMapMonotonic
+    fold'              = IntPSQ.fold'
+    valid              = IntPSQ.valid
 
 instance forall k. Ord k => PSQ (OrdPSQ.OrdPSQ k) where
     type Key (OrdPSQ.OrdPSQ k) = k
 
-    null       = OrdPSQ.null
-    size       = OrdPSQ.size
-    member     = OrdPSQ.member
-    lookup     = OrdPSQ.lookup
-    findMin    = OrdPSQ.findMin
-    empty      = OrdPSQ.empty
-    singleton  = OrdPSQ.singleton
-    insert     = OrdPSQ.insert
-    delete     = OrdPSQ.delete
-    deleteMin  = OrdPSQ.deleteMin
-    alter      = OrdPSQ.alter
-    alterMin   = OrdPSQ.alterMin
-    fromList   = OrdPSQ.fromList
-    toList     = OrdPSQ.toList
-    keys       = OrdPSQ.keys
-    insertView = OrdPSQ.insertView
-    deleteView = OrdPSQ.deleteView
-    minView    = OrdPSQ.minView
-    atMostView = OrdPSQ.atMostView
-    map        = OrdPSQ.map
-    fold'      = OrdPSQ.fold'
-    valid      = OrdPSQ.valid
+    null               = OrdPSQ.null
+    size               = OrdPSQ.size
+    member             = OrdPSQ.member
+    lookup             = OrdPSQ.lookup
+    findMin            = OrdPSQ.findMin
+    empty              = OrdPSQ.empty
+    singleton          = OrdPSQ.singleton
+    insert             = OrdPSQ.insert
+    delete             = OrdPSQ.delete
+    deleteMin          = OrdPSQ.deleteMin
+    alter              = OrdPSQ.alter
+    alterMin           = OrdPSQ.alterMin
+    fromList           = OrdPSQ.fromList
+    toList             = OrdPSQ.toList
+    keys               = OrdPSQ.keys
+    insertView         = OrdPSQ.insertView
+    deleteView         = OrdPSQ.deleteView
+    minView            = OrdPSQ.minView
+    atMostView         = OrdPSQ.atMostView
+    map                = OrdPSQ.map
+    unsafeMapMonotonic = OrdPSQ.unsafeMapMonotonic
+    fold'              = OrdPSQ.fold'
+    valid              = OrdPSQ.valid
 
 instance forall k. (Hashable k, Ord k) => PSQ (HashPSQ.HashPSQ k) where
     type Key (HashPSQ.HashPSQ k) = k
 
-    null       = HashPSQ.null
-    size       = HashPSQ.size
-    member     = HashPSQ.member
-    lookup     = HashPSQ.lookup
-    findMin    = HashPSQ.findMin
-    empty      = HashPSQ.empty
-    singleton  = HashPSQ.singleton
-    insert     = HashPSQ.insert
-    delete     = HashPSQ.delete
-    deleteMin  = HashPSQ.deleteMin
-    alter      = HashPSQ.alter
-    alterMin   = HashPSQ.alterMin
-    fromList   = HashPSQ.fromList
-    toList     = HashPSQ.toList
-    keys       = HashPSQ.keys
-    insertView = HashPSQ.insertView
-    deleteView = HashPSQ.deleteView
-    minView    = HashPSQ.minView
-    atMostView = HashPSQ.atMostView
-    map        = HashPSQ.map
-    fold'      = HashPSQ.fold'
-    valid      = HashPSQ.valid
+    null               = HashPSQ.null
+    size               = HashPSQ.size
+    member             = HashPSQ.member
+    lookup             = HashPSQ.lookup
+    findMin            = HashPSQ.findMin
+    empty              = HashPSQ.empty
+    singleton          = HashPSQ.singleton
+    insert             = HashPSQ.insert
+    delete             = HashPSQ.delete
+    deleteMin          = HashPSQ.deleteMin
+    alter              = HashPSQ.alter
+    alterMin           = HashPSQ.alterMin
+    fromList           = HashPSQ.fromList
+    toList             = HashPSQ.toList
+    keys               = HashPSQ.keys
+    insertView         = HashPSQ.insertView
+    deleteView         = HashPSQ.deleteView
+    minView            = HashPSQ.minView
+    atMostView         = HashPSQ.atMostView
+    map                = HashPSQ.map
+    unsafeMapMonotonic = HashPSQ.unsafeMapMonotonic
+    fold'              = HashPSQ.fold'
+    valid              = HashPSQ.valid
diff --git a/tests/Data/PSQ/Class/Tests.hs b/tests/Data/PSQ/Class/Tests.hs
--- a/tests/Data/PSQ/Class/Tests.hs
+++ b/tests/Data/PSQ/Class/Tests.hs
@@ -52,28 +52,29 @@
     , testCase "fromList" (untag' test_fromList)
     , testCase "foldr"    (untag' test_foldr)
 
-    , testProperty "show"             (untag' prop_show)
-    , testProperty "rnf"              (untag' prop_rnf)
-    , testProperty "size"             (untag' prop_size)
-    , testProperty "singleton"        (untag' prop_singleton)
-    , testProperty "memberLookup"     (untag' prop_memberLookup)
-    , testProperty "insertLookup"     (untag' prop_insertLookup)
-    , testProperty "insertDelete"     (untag' prop_insertDelete)
-    , testProperty "insertDeleteView" (untag' prop_insertDeleteView)
-    , testProperty "deleteNonMember"  (untag' prop_deleteNonMember)
-    , testProperty "deleteMin"        (untag' prop_deleteMin)
-    , testProperty "alter"            (untag' prop_alter)
-    , testProperty "alterMin"         (untag' prop_alterMin)
-    , testProperty "toList"           (untag' prop_toList)
-    , testProperty "keys"             (untag' prop_keys)
-    , testProperty "insertView"       (untag' prop_insertView)
-    , testProperty "deleteView"       (untag' prop_deleteView)
-    , testProperty "map"              (untag' prop_map)
-    , testProperty "fmap"             (untag' prop_fmap)
-    , testProperty "fold'"            (untag' prop_fold')
-    , testProperty "foldr"            (untag' prop_foldr)
-    , testProperty "valid"            (untag' prop_valid)
-    , testProperty "atMostView"       (untag' prop_atMostView)
+    , testProperty "show"               (untag' prop_show)
+    , testProperty "rnf"                (untag' prop_rnf)
+    , testProperty "size"               (untag' prop_size)
+    , testProperty "singleton"          (untag' prop_singleton)
+    , testProperty "memberLookup"       (untag' prop_memberLookup)
+    , testProperty "insertLookup"       (untag' prop_insertLookup)
+    , testProperty "insertDelete"       (untag' prop_insertDelete)
+    , testProperty "insertDeleteView"   (untag' prop_insertDeleteView)
+    , testProperty "deleteNonMember"    (untag' prop_deleteNonMember)
+    , testProperty "deleteMin"          (untag' prop_deleteMin)
+    , testProperty "alter"              (untag' prop_alter)
+    , testProperty "alterMin"           (untag' prop_alterMin)
+    , testProperty "toList"             (untag' prop_toList)
+    , testProperty "keys"               (untag' prop_keys)
+    , testProperty "insertView"         (untag' prop_insertView)
+    , testProperty "deleteView"         (untag' prop_deleteView)
+    , testProperty "map"                (untag' prop_map)
+    , testProperty "unsafeMapMonotonic" (untag' prop_unsafeMapMonotonic)
+    , testProperty "fmap"               (untag' prop_fmap)
+    , testProperty "fold'"              (untag' prop_fold')
+    , testProperty "foldr"              (untag' prop_foldr)
+    , testProperty "valid"              (untag' prop_valid)
+    , testProperty "atMostView"         (untag' prop_atMostView)
     ]
   where
     untag' :: Tagged psq test -> test
@@ -397,6 +398,20 @@
         fromList (List.map (\(k, p, x) -> (k, p, f k p x)) (toList t))
   where
     f k p x = if fromEnum k > p then x else 'a'
+
+prop_unsafeMapMonotonic
+    :: forall psq. (PSQ psq, TestKey (Key psq),
+                    Arbitrary (psq Int Char),
+                    Eq (psq Int Char),
+                    Show (psq Int Char))
+    => Tagged psq (psq Int Char -> Bool)
+prop_unsafeMapMonotonic = Tagged $ \t ->
+    let t' = unsafeMapMonotonic f (t :: psq Int Char) :: psq Int Char in
+    valid t' &&
+    t' == fromList (List.map (\(k, p, x) -> let (p', x') = f k p x in (k, p', x'))
+                           (toList t))
+  where
+    f k p x = (p + 1, if fromEnum k > p then x else 'a')
 
 prop_fmap
     :: forall psq. (PSQ psq, TestKey (Key psq),