diff --git a/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs b/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs
index 59b444a05f24f7ff227fcde445daa7851a400913..2f802aefa40a8cca443c8800b0e88db68e93e162 100644
--- a/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs
+++ b/haddock-api/src/Haddock/Backends/Xhtml/Decl.hs
@@ -269,6 +269,11 @@ ppTyFamHeader summary associated d@(FamilyDecl { fdInfo = info
   (case injectivity of
      Nothing                   -> noHtml
      Just (L _ injectivityAnn) -> ppInjectivityAnn unicode qual injectivityAnn
+  ) <+>
+
+  (case info of
+     ClosedTypeFamily _ -> keyword "where ..."
+     _                  -> mempty
   )
 
 ppResultSig :: FamilyResultSig DocName -> Unicode -> Qualification -> Html