diff --git a/ghc-heap-view.cabal b/ghc-heap-view.cabal
--- a/ghc-heap-view.cabal
+++ b/ghc-heap-view.cabal
@@ -1,5 +1,5 @@
 Name:                ghc-heap-view
-Version:             0.5.0.1
+Version:             0.5.1
 Synopsis:            Extract the heap representation of Haskell values and thunks
 Description:
   This library provides functions to introspect the Haskell heap, for example
@@ -65,7 +65,7 @@
     containers,
     transformers,
     template-haskell,
-    bytestring (>= 0.10),
+    bytestring >= 0.10,
     binary,
     ghc
   C-Sources: cbits/HeapView.c cbits/HeapViewPrim.cmm
diff --git a/src/GHC/AssertNF.hs b/src/GHC/AssertNF.hs
--- a/src/GHC/AssertNF.hs
+++ b/src/GHC/AssertNF.hs
@@ -20,6 +20,7 @@
     assertNFNamed,
     assertNFHere,
     disableAssertNF,
+    isNF,
     )
 where
 
@@ -121,3 +122,30 @@
 -- to 'assertNF' and its variants to noops.
 disableAssertNF :: IO ()
 disableAssertNF = writeIORef enabledRef False
+
+-- | A variant of 'assertNF' that does not print anything and just returns
+-- 'True' if the value is in normal form, or 'False' otherwise. This function
+-- is not affected by 'disableAssertNF'.
+isNF :: a -> IO Bool
+isNF x = isNFBoxed (asBox x)
+
+isNFBoxed :: Box -> IO Bool
+isNFBoxed b = do
+    c <- getBoxedClosureData b
+    nf <- isHNF c
+    if nf
+    then do
+        c' <- getBoxedClosureData b
+        allM isNFBoxed (allPtrs c')
+    else do
+        return False
+
+-- From Control.Monad.Loops in monad-loops, but I'd like to avoid too many
+-- trivial dependencies
+allM :: (Monad m) => (a -> m Bool) -> [a] -> m Bool
+allM _ []       = return True
+allM p (x:xs)   = do
+        q <- p x
+        if q
+                then allM p xs
+                else return False