diff --git a/dequeue.cabal b/dequeue.cabal
--- a/dequeue.cabal
+++ b/dequeue.cabal
@@ -1,7 +1,7 @@
 Build-Type: Simple
 Name: dequeue
 Category: Data Structures
-Version: 0.1.7
+Version: 0.1.8
 Cabal-Version: >= 1.2
 Synopsis: A typeclass and an implementation for double-ended queues.
 Description:
@@ -26,4 +26,5 @@
     Main-Is: Tests.hs
     Hs-Source-Dirs: src
     Build-Depends: base < 5, QuickCheck
+    GHC-Options: -Wall
 
diff --git a/src/Data/Dequeue.hs b/src/Data/Dequeue.hs
--- a/src/Data/Dequeue.hs
+++ b/src/Data/Dequeue.hs
@@ -67,6 +67,10 @@
     empty :: q a
     -- | Returns 'True' if this queue is empty.
     null :: q a -> Bool
+#if !MIN_VERSION_base(4,8,0)
+        -- | Returns the number of elements in this queue.
+    length :: q a -> Int
+#endif
     -- | Returns the item on the front of the queue.
     first :: q a -> Maybe a
     -- | Returns the item on the end of the queue.
@@ -197,12 +201,17 @@
     foldl f a (BankersDequeue _ front _ rear) = foldl f a (front ++ reverse rear)
     foldr1 f (BankersDequeue _ front _ rear) = foldr1 f (front ++ reverse rear)
     foldl1 f (BankersDequeue _ front _ rear) = foldl1 f (front ++ reverse rear)
+#if MIN_VERSION_base(4,8,0)
     length (BankersDequeue sizeF _ sizeR _) = sizeF + sizeR
+#endif
 
 instance Dequeue BankersDequeue where
     empty = BankersDequeue 0 [] 0 []
     null (BankersDequeue 0 [] 0 []) = True
     null _ = False
+#if !MIN_VERSION_base(4,8,0)
+    length (BankersDequeue sizeF _ sizeR _) = sizeF + sizeR
+#endif
     first (BankersDequeue _ [] _ [x]) = Just x
     first (BankersDequeue _ front _ _) =  headMay front
     last (BankersDequeue _ [x] _ []) = Just x
@@ -316,35 +325,40 @@
 
 -- | Validates that a 'BankersDequeue' remains balanced despite repeated
 --   pushes to the front.
-prop_push_front_bq_balance :: BankersDequeue Int -> Int -> Bool
-prop_push_front_bq_balance q count =
-    let push _ = (flip pushFront) 0
-        q' = foldr push q [0 .. count] in
+prop_push_front_bq_balance :: BankersDequeue Int -> Int -> Gen Prop
+prop_push_front_bq_balance q count = count < qcLimit ==>
+    let push queue _ = pushFront queue 0
+        q' = foldl push q [0 .. count] in
     balanced q'
 
 -- | Validates that a 'BankersDequeue' remains balanced despite repeated
 --   pushes to the back.
-prop_push_back_bq_balance :: BankersDequeue Int -> Int -> Bool
-prop_push_back_bq_balance q count =
-    let push _ = (flip pushBack) 0
-        q' = foldr push q [0 .. count] in
+prop_push_back_bq_balance :: BankersDequeue Int -> Int -> Gen Prop
+prop_push_back_bq_balance q count = count < qcLimit ==>
+    let push queue _ = pushBack queue 0
+        q' = foldl push q [0 .. count] in
     balanced q'
 
 -- | Validates that a 'BankersDequeue' remains balanced despite repeated
 --   pops from the front.
-prop_pop_front_bq_balance :: BankersDequeue Int -> Int -> Bool
-prop_pop_front_bq_balance q count =
-    let pop _ queue = (fromJustDef queue . liftM snd . popFront) queue
-        q' = foldr pop q [0 .. count] in
+prop_pop_front_bq_balance :: BankersDequeue Int -> Int -> Gen Prop
+prop_pop_front_bq_balance q count = count < qcLimit ==>
+    let pop queue _ = (fromJustDef queue . liftM snd . popFront) queue
+        q' = foldl pop q [0 .. count] in
     balanced q'
 
 -- | Validates that a 'BankersDequeue' remains balanced despite repeated
 --   pops from the back.
-prop_pop_back_bq_balance :: BankersDequeue Int -> Int -> Bool
-prop_pop_back_bq_balance q count =
-    let pop _ queue = (fromJustDef queue . liftM snd . popBack) queue
-        q' = foldr pop q [0 .. count] in
+prop_pop_back_bq_balance :: BankersDequeue Int -> Int -> Gen Prop
+prop_pop_back_bq_balance q count = count < qcLimit ==>
+    let pop queue _ = (fromJustDef queue . liftM snd . popBack) queue
+        q' = foldl pop q [0 .. count] in
     balanced q'
+
+-- | Limit quickcheck tests to this size of dequeue, to keep test time and
+--   memory usage reasonable.
+qcLimit :: Int
+qcLimit = 10 ^ (6 :: Int)
 
 -- | Validates that a 'BankersDequeue' has read and show instances that are
 --   the inverse of each other.