diff --git a/heist.cabal b/heist.cabal
--- a/heist.cabal
+++ b/heist.cabal
@@ -1,5 +1,5 @@
 name:           heist
-version:        0.14.1.2
+version:        0.14.1.3
 synopsis:       An Haskell template system supporting both HTML5 and XML.
 description:
     Heist is a powerful template system that supports both HTML5 and XML.
diff --git a/src/Heist.hs b/src/Heist.hs
--- a/src/Heist.hs
+++ b/src/Heist.hs
@@ -202,7 +202,7 @@
 -- | Creates an empty HeistState.
 emptyHS :: HE.KeyGen -> HeistState m
 emptyHS kg = HeistState Map.empty Map.empty Map.empty Map.empty Map.empty
-                        True [] 0 [] Nothing kg False Html "" [] False
+                        True [] 0 [] Nothing kg False Html "" [] False 0
 
 
 ------------------------------------------------------------------------------
diff --git a/src/Heist/Compiled/Internal.hs b/src/Heist/Compiled/Internal.hs
--- a/src/Heist/Compiled/Internal.hs
+++ b/src/Heist/Compiled/Internal.hs
@@ -29,6 +29,7 @@
 import qualified Data.Text                          as T
 import qualified Data.Text.Encoding                 as T
 import qualified Data.Vector                        as V
+import           Text.Printf
 import qualified Text.XmlHtml                       as X
 import qualified Text.XmlHtml.HTML.Meta             as X
 ------------------------------------------------------------------------------
@@ -161,12 +162,28 @@
     -> IO (Either [String] (HeistState n))
 compileTemplates hs = do
     (tmap, hs') <- runHeistT compileTemplates' (X.TextNode "") hs
+    let pre = _splicePrefix hs'
+    let nsErr = if not (T.null pre) && (_numNamespacedTags hs' == 0)
+                  then Left [noNamespaceSplicesMsg $ T.unpack pre]
+                  else Right ()
     return $ case _spliceErrors hs' of
-               [] -> Right $! hs { _compiledTemplateMap = tmap }
-               es -> Left $ map T.unpack es
+               [] -> nsErr >> (Right $! hs { _compiledTemplateMap = tmap })
+               es -> Left $ either (++) (const id) nsErr $ map T.unpack es
 
 
 ------------------------------------------------------------------------------
+noNamespaceSplicesMsg :: String -> String
+noNamespaceSplicesMsg pre = unwords
+    [ printf "You are using a namespace of '%s', but you don't have any" ns
+    , printf "tags starting with '%s'.  If you have not defined any" pre
+    , "splices, then change your namespace to the empty string to get rid"
+    , "of this message."
+    ]
+  where
+    ns = reverse $ drop 1 $ reverse pre
+
+
+------------------------------------------------------------------------------
 compileTemplates'
     :: Monad n
     => HeistT n IO (H.HashMap TPath ([Chunk n], MIMEType))
@@ -253,6 +270,9 @@
 -- compileNode to generate the appropriate runtime computation.
 runNode :: Monad n => X.Node -> Splice n
 runNode node = localParamNode (const node) $ do
+    pre <- getsHS _splicePrefix
+    let hasPrefix = (T.isPrefixOf pre `fmap` X.tagName node) == Just True
+    when (not (T.null pre) && hasPrefix) incNamespacedTags
     isStatic <- subtreeIsStatic node
     markup <- getsHS _curMarkup
     if isStatic
diff --git a/src/Heist/Internal/Types/HeistState.hs b/src/Heist/Internal/Types/HeistState.hs
--- a/src/Heist/Internal/Types/HeistState.hs
+++ b/src/Heist/Internal/Types/HeistState.hs
@@ -204,6 +204,7 @@
     -- correspond to a bound splice.  When not using a namespace, this flag is
     -- ignored.
     , _errorNotBound       :: Bool
+    , _numNamespacedTags   :: Int
 #if MIN_VERSION_base(4,7,0)
 } deriving (Typeable)
 #else
@@ -532,6 +533,13 @@
 modRecursionDepth :: Monad m => (Int -> Int) -> HeistT n m ()
 modRecursionDepth f =
     modifyHS (\st -> st { _recursionDepth = f (_recursionDepth st) })
+
+
+------------------------------------------------------------------------------
+-- | Increments the namespaced tag count
+incNamespacedTags :: Monad m => HeistT n m ()
+incNamespacedTags =
+    modifyHS (\st -> st { _numNamespacedTags = _numNamespacedTags st + 1 })
 
 
 ------------------------------------------------------------------------------
diff --git a/test/suite/Heist/Compiled/Tests.hs b/test/suite/Heist/Compiled/Tests.hs
--- a/test/suite/Heist/Compiled/Tests.hs
+++ b/test/suite/Heist/Compiled/Tests.hs
@@ -18,6 +18,7 @@
 ------------------------------------------------------------------------------
 import           Heist
 import           Heist.Compiled
+import           Heist.Compiled.Internal
 import           Heist.Internal.Types
 import           Heist.Tutorial.CompiledSplices
 import           Heist.TestCommon
@@ -35,6 +36,7 @@
         , testCase     "compiled/namespace3"    namespaceTest3
         , testCase     "compiled/namespace4"    namespaceTest4
         , testCase     "compiled/namespace5"    namespaceTest5
+        , testCase     "compiled/no-ns-splices" noNsSplices
         , testCase     "compiled/nsbind"        nsBindTest
         , testCase     "compiled/nsbinderr"     nsBindErrorTest
         ]
@@ -131,6 +133,25 @@
         return $ toByteString b
 
     H.assertEqual "namespace test" (Left ["templates/namespaces.tpl: No splice bound for h:foo"]) res
+
+------------------------------------------------------------------------------
+-- | The templates-no-ns directory should have no tags beginning with h: so
+-- this test will throw an error.
+noNsSplices :: IO ()
+noNsSplices = do
+    res <- runEitherT $ do
+        hs <- initHeist hc
+        runner <- noteT ["Error rendering"] $ hoistMaybe $
+                    renderTemplate hs "test"
+        b <- lift $ fst runner
+        return $ toByteString b
+
+    H.assertEqual "namespace test" (Left [noNamespaceSplicesMsg "h:"]) res
+  where
+    hc = HeistConfig sc "h" True
+    sc = mempty & scLoadTimeSplices .~ defaultLoadTimeSplices
+                & scCompiledSplices .~ ("foo" ## return (yieldPureText "aoeu"))
+                & scTemplateLocations .~ [loadTemplates "templates-no-ns"]
 
 
 nsBindTemplateHC :: HeistConfig IO