diff --git a/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.dcl b/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.dcl
index dfb9e1935cc234c855f50c68dfed15c9d6b973f1..8374ba8ceb31beb4866dd596c7fad06132e62d61 100644
--- a/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.dcl
+++ b/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.dcl
@@ -10,7 +10,7 @@ import Data.Graph.Inductive.Graph
   , key :: Int
   }
 
-instance == (NodeMap a) | == a
+instance == (NodeMap a) | Eq a
 
 // | Create a new, empty mapping.
 new :: NodeMap a
diff --git a/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.icl b/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.icl
index 2d4b071dd4b539b9eb930c5e9218f4f416f659d8..e75c5552c43472ec729419a14e6026702009d035 100644
--- a/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.icl
+++ b/src/libraries/OS-Independent/Data/Graph/Inductive/NodeMap.icl
@@ -19,7 +19,7 @@ import qualified Data.List as DL
   , key :: Int
   }
 
-instance == (NodeMap a) | == a where
+instance == (NodeMap a) | Eq a where
   (==) {map, key} {map = map`, key = key`} = key == key` && map == map`
 
 // | Create a new, empty mapping.