5 files changed, 15 insertions, 10 deletions
diff --git a/src/Hakyll/Core/Compiler/Internal.hs b/src/Hakyll/Core/Compiler/Internal.hs
index 259cd35..8424d69 100644
--- a/src/Hakyll/Core/Compiler/Internal.hs
+++ b/src/Hakyll/Core/Compiler/Internal.hs
@@ -248,5 +248,6 @@ compilerGetMatches :: Pattern -> Compiler [Identifier]
 compilerGetMatches pattern = do
     universe <- compilerUniverse <$> compilerAsk
     let matching = filterMatches pattern $ S.toList universe
-    compilerTellDependencies [PatternDependency pattern matching]
+        set'     = S.fromList matching
+    compilerTellDependencies [PatternDependency pattern set']
     return matching
diff --git a/src/Hakyll/Core/Dependencies.hs b/src/Hakyll/Core/Dependencies.hs
index 7597e61..ebb6fd0 100644
--- a/src/Hakyll/Core/Dependencies.hs
+++ b/src/Hakyll/Core/Dependencies.hs
@@ -32,7 +32,7 @@ import           Hakyll.Core.Identifier.Pattern
 
 --------------------------------------------------------------------------------
 data Dependency
-    = PatternDependency Pattern [Identifier]
+    = PatternDependency Pattern (Set Identifier)
     | IdentifierDependency Identifier
     deriving (Show, Typeable)
 
@@ -91,7 +91,7 @@ dependenciesFor id' = do
     return $ concatMap dependenciesFor' $ fromMaybe [] $ M.lookup id' facts
   where
     dependenciesFor' (IdentifierDependency i) = [i]
-    dependenciesFor' (PatternDependency _ is) = is
+    dependenciesFor' (PatternDependency _ is) = S.toList is
 
 
 --------------------------------------------------------------------------------
@@ -116,7 +116,7 @@ checkChangedPatterns = do
     go _   ds (IdentifierDependency i) = return $ IdentifierDependency i : ds
     go id' ds (PatternDependency p ls) = do
         universe <- ask
-        let ls' = filterMatches p universe
+        let ls' = S.fromList $ filterMatches p universe
         if ls == ls'
             then return $ PatternDependency p ls : ds
             else do
diff --git a/src/Hakyll/Core/Metadata.hs b/src/Hakyll/Core/Metadata.hs
index 7902b94..3ce854f 100644
--- a/src/Hakyll/Core/Metadata.hs
+++ b/src/Hakyll/Core/Metadata.hs
@@ -12,6 +12,7 @@ module Hakyll.Core.Metadata
 import           Control.Monad                  (forM)
 import           Data.Map                       (Map)
 import qualified Data.Map                       as M
+import qualified Data.Set                       as S
 
 
 --------------------------------------------------------------------------------
@@ -60,4 +61,4 @@ getMetadataField' identifier key = do
 makePatternDependency :: MonadMetadata m => Pattern -> m Dependency
 makePatternDependency pattern = do
     matches' <- getMatches pattern
-    return $ PatternDependency pattern matches'
+    return $ PatternDependency pattern (S.fromList matches')
diff --git a/src/Hakyll/Web/Paginate.hs b/src/Hakyll/Web/Paginate.hs
index eafd3a9..1af792e 100644
--- a/src/Hakyll/Web/Paginate.hs
+++ b/src/Hakyll/Web/Paginate.hs
@@ -15,6 +15,7 @@ import           Control.Monad                  (forM_)
 import           Data.List                      (unfoldr)
 import qualified Data.Map                       as M
 import           Data.Monoid                    (mconcat)
+import qualified Data.Set                       as S
 import           Text.Printf                    (printf)
 
 
@@ -58,7 +59,7 @@ buildPaginate pattern = do
                 "invalid page number: " ++ show pn
 
     return $ Paginate pagPages pagPlaces makeId
-        (PatternDependency pattern idents)
+        (PatternDependency pattern (S.fromList idents))
 
 
 --------------------------------------------------------------------------------
@@ -81,7 +82,7 @@ buildPaginateWith n makeId pattern = do
             [(makeId i, i) | i <- [1 .. nPages]]
 
     return $ Paginate (M.fromList paginatePages') (M.fromList pagPlaces') makeId
-        (PatternDependency pattern idents)
+        (PatternDependency pattern (S.fromList idents))
 
 
 --------------------------------------------------------------------------------
diff --git a/src/Hakyll/Web/Tags.hs b/src/Hakyll/Web/Tags.hs
index 0fa182c..0887856 100644
--- a/src/Hakyll/Web/Tags.hs
+++ b/src/Hakyll/Web/Tags.hs
@@ -71,6 +71,7 @@ import qualified Data.Map                        as M
 import           Data.Maybe                      (catMaybes, fromMaybe)
 import           Data.Monoid                     (mconcat)
 import           Data.Ord                        (comparing)
+import qualified Data.Set                        as S
 import           System.FilePath                 (takeBaseName, takeDirectory)
 import           Text.Blaze.Html                 (toHtml, toValue, (!))
 import           Text.Blaze.Html.Renderer.String (renderHtml)
@@ -124,7 +125,8 @@ buildTagsWith :: MonadMetadata m
 buildTagsWith f pattern makeId = do
     ids    <- getMatches pattern
     tagMap <- foldM addTags M.empty ids
-    return $ Tags (M.toList tagMap) makeId (PatternDependency pattern ids)
+    let set' = S.fromList ids
+    return $ Tags (M.toList tagMap) makeId (PatternDependency pattern set')
   where
     -- Create a tag map for one page
     addTags tagMap id' = do
@@ -148,8 +150,8 @@ buildCategories = buildTagsWith getCategory
 tagsRules :: Tags -> (String -> Pattern -> Rules ()) -> Rules ()
 tagsRules tags rules =
     forM_ (tagsMap tags) $ \(tag, identifiers) ->
-        create [tagsMakeId tags tag] $
-            rulesExtraDependencies [tagsDependency tags] $
+        rulesExtraDependencies [tagsDependency tags] $
+            create [tagsMakeId tags tag] $
                 rules tag $ fromList identifiers