3 files changed, 7 insertions, 5 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')