diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+5.8.1.1
+-------
+
+* Data.Graph.Inductive.Query.Dominators.{dom,iDom} could fail for some
+  graphs (issue #109, regression in 5.8.1.0).
+
 5.8.1.0
 -------
 
diff --git a/Data/Graph/Inductive/Query/Dominators.hs b/Data/Graph/Inductive/Query/Dominators.hs
--- a/Data/Graph/Inductive/Query/Dominators.hs
+++ b/Data/Graph/Inductive/Query/Dominators.hs
@@ -17,16 +17,17 @@
 import           Data.Graph.Inductive.Query.DFS
 import           Data.IntMap                    (IntMap)
 import qualified Data.IntMap                    as I
+import           Data.Maybe (mapMaybe)
 import           Data.Tree                      (Tree (..))
 import qualified Data.Tree                      as T
 
 {-# ANN iDom "HLint: ignore Use ***" #-}
--- | return immediate dominators for each node of a graph, given a root
+-- | return immediate dominators for each reachable node of a graph, given a root
 iDom :: (Graph gr) => gr a b -> Node -> [(Node,Node)]
 iDom g root = let (result, toNode, _) = idomWork g root
               in  map (\(a, b) -> (toNode ! a, toNode ! b)) (assocs result)
 
--- | return the set of dominators of the nodes of a graph, given a root
+-- | return the set of dominators of the reachable nodes of a graph, given a root
 dom :: (Graph gr) => gr a b -> Node -> [(Node,[Node])]
 dom g root = let
     (iD, toNode, fromNode) = idomWork g root
@@ -62,7 +63,7 @@
     fromNode = I.unionWith const (I.fromList (zip (T.flatten tree) (T.flatten ntree))) (I.fromList (zip nds (repeat (-1))))
     -- toNode translates internal nodes to graph nodes
     toNode = array (0, s-1) (zip (T.flatten ntree) (T.flatten tree))
-    preds = array (1, s-1) [(i, filter (/= -1) (map (fromNode I.!)
+    preds = array (1, s-1) [(i, filter (/= -1) (mapMaybe (`I.lookup` fromNode)
                             (pre g (toNode ! i)))) | i <- [1..s-1]]
     -- iteratively improve the approximation to find iDom.
     iD = fixEq (refineIDom preds) iD0
diff --git a/Data/Graph/Inductive/Query/TransClos.hs b/Data/Graph/Inductive/Query/TransClos.hs
--- a/Data/Graph/Inductive/Query/TransClos.hs
+++ b/Data/Graph/Inductive/Query/TransClos.hs
@@ -18,8 +18,8 @@
     outU gr  = map toEdge . out gr
 
 {-|
-Finds the transitive, reflexive closure of a directed graph.
-Given a graph G=(V,E), its transitive closure is the graph:
+Finds the reflexive-transitive closure of a directed graph.
+Given a graph G=(V,E), its reflexive-transitive closure is the graph:
 G* = (V,E*) where E*={(i,j): i,j in V and either i = j or there is a path from i to j in G}
 -}
 trc :: (DynGraph gr) => gr a b -> gr a ()
@@ -30,7 +30,7 @@
 
 {-|
 Finds the reflexive closure of a directed graph.
-Given a graph G=(V,E), its transitive closure is the graph:
+Given a graph G=(V,E), its reflexive closure is the graph:
 G* = (V,Er union E) where Er = {(i,i): i in V}
 -}
 rc :: (DynGraph gr) => gr a b -> gr a ()
diff --git a/fgl.cabal b/fgl.cabal
--- a/fgl.cabal
+++ b/fgl.cabal
@@ -1,5 +1,5 @@
 name:          fgl
-version:       5.8.1.0
+version:       5.8.1.1
 license:       BSD3
 license-file:  LICENSE
 author:        Martin Erwig, Ivan Lazar Miljenovic
@@ -20,7 +20,7 @@
 tested-with:   GHC == 7.2.2,  GHC == 7.4.2, GHC == 7.6.3, GHC == 7.8.4,
                GHC == 7.10.3, GHC == 8.0.2, GHC == 8.2.2, GHC == 8.4.3,
                GHC == 8.6.2,  GHC == 8.8.2, GHC == 8.10.7, GHC == 9.0.2,
-               GHC == 9.2.3, GHC == 9.4.2
+               GHC == 9.2.4, GHC == 9.4.4
 
 source-repository head
     type:         git
diff --git a/test/Data/Graph/Inductive/Query/Properties.hs b/test/Data/Graph/Inductive/Query/Properties.hs
--- a/test/Data/Graph/Inductive/Query/Properties.hs
+++ b/test/Data/Graph/Inductive/Query/Properties.hs
@@ -149,6 +149,9 @@
   it "directed reachable components dom" $
     sortIt (dom domGraph2 1) `shouldMatchList` [ (1, [1]) ]
 
+  it "unreachable nodes dom" $
+    sortIt (dom domGraph3 1) `shouldMatchList` [(1,[1]), (2,[1,2])]
+
   where
     sortIt = map (second sort)
 
@@ -181,6 +184,9 @@
                      , (2,2)
                      ]
 
+-- From #109: 1 -> 2 <- 3
+domGraph3 :: Gr () ()
+domGraph3 = mkUGraph [1..3] [(1,2), (3,2)]
 
 -- -----------------------------------------------------------------------------
 -- GVD
diff --git a/test/TestSuite.hs b/test/TestSuite.hs
--- a/test/TestSuite.hs
+++ b/test/TestSuite.hs
@@ -79,7 +79,7 @@
     propType  "subgraph"          valid_subgraph
 
   where
-    proxyProp str = prop str . ($p)
+    proxyProp str = prop str . ($ p)
 
     propType :: (Testable pr) => String -> (GraphType gr -> pr) -> Spec
     propType = prop
@@ -126,7 +126,7 @@
     propP "tc"         test_tc
     propP "rc"         test_rc
   where
-    propP str = prop str . ($p)
+    propP str = prop str . ($ p)
 
     p :: PatriciaTreeP
     p = Proxy