diff --git a/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs b/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs
index e020b90991..2d0bf7a398 100644
--- a/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs
+++ b/haddock-api/src/Haddock/Backends/Xhtml/Layout.hs
@@ -199,7 +199,7 @@ subInstances :: Qualification
              -> [(SubDecl,Located DocName)] -> Html
 subInstances qual nm lnks splice = maybe noHtml wrap . instTable
   where
-    wrap contents = subSection (collapseDetails id_ DetailsOpen (summary +++ contents))
+    wrap contents = subSection (collapseDetails id_ DetailsClosed (summary +++ contents))
     instTable = subTableSrc qual lnks splice
     subSection = thediv ! [theclass "subs instances"]
     summary = thesummary << "Instances"
diff --git a/html-test/ref/Bug26.html b/html-test/ref/Bug26.html
index 376c2ce6b3..62a3af3166 100644
--- a/html-test/ref/Bug26.html
+++ b/html-test/ref/Bug26.html
@@ -151,7 +151,7 @@
 	      ></div
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:C" open="open"
+	  ><details id="i:C"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/Bug294.html b/html-test/ref/Bug294.html
index 87a037318c..89271104bc 100644
--- a/html-test/ref/Bug294.html
+++ b/html-test/ref/Bug294.html
@@ -51,7 +51,7 @@
 	    >#</a
 	    ></p
 	  ><div class="subs instances"
-	  ><details id="i:A" open="open"
+	  ><details id="i:A"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -179,7 +179,7 @@
 	    >#</a
 	    ></p
 	  ><div class="subs instances"
-	  ><details id="i:DP" open="open"
+	  ><details id="i:DP"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/Bug613.html b/html-test/ref/Bug613.html
index 765f18e1b2..61db909521 100644
--- a/html-test/ref/Bug613.html
+++ b/html-test/ref/Bug613.html
@@ -97,7 +97,7 @@
 	      ></p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Functor" open="open"
+	  ><details id="i:Functor"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -209,7 +209,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:ThreeVars" open="open"
+	  ><details id="i:ThreeVars"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/Bug7.html b/html-test/ref/Bug7.html
index ba1a4e26a7..6ac467a540 100644
--- a/html-test/ref/Bug7.html
+++ b/html-test/ref/Bug7.html
@@ -100,7 +100,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Foo" open="open"
+	  ><details id="i:Foo"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -150,7 +150,7 @@
 	    >The Bar class</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Bar" open="open"
+	  ><details id="i:Bar"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/Hash.html b/html-test/ref/Hash.html
index 21004e20da..65b70fe203 100644
--- a/html-test/ref/Hash.html
+++ b/html-test/ref/Hash.html
@@ -284,7 +284,7 @@
 	      ></div
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Hash" open="open"
+	  ><details id="i:Hash"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/HiddenInstances.html b/html-test/ref/HiddenInstances.html
index b35866493d..64606cbde8 100644
--- a/html-test/ref/HiddenInstances.html
+++ b/html-test/ref/HiddenInstances.html
@@ -75,7 +75,7 @@
 	    >Should be visible</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:VisibleClass" open="open"
+	  ><details id="i:VisibleClass"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -149,7 +149,7 @@
 	    >Should be visible</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:VisibleData" open="open"
+	  ><details id="i:VisibleData"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/HiddenInstancesB.html b/html-test/ref/HiddenInstancesB.html
index d2f7b74dc8..ad61143d30 100644
--- a/html-test/ref/HiddenInstancesB.html
+++ b/html-test/ref/HiddenInstancesB.html
@@ -75,7 +75,7 @@
 	    >Should be visible</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Foo" open="open"
+	  ><details id="i:Foo"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -123,7 +123,7 @@
 	    >Should be visible</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Bar" open="open"
+	  ><details id="i:Bar"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/Instances.html b/html-test/ref/Instances.html
index 84c9498f01..823c24fbd0 100644
--- a/html-test/ref/Instances.html
+++ b/html-test/ref/Instances.html
@@ -65,7 +65,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:-60--126--126-" open="open"
+	  ><details id="i:-60--126--126-"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -165,7 +165,7 @@
 	      ></p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Foo" open="open"
+	  ><details id="i:Foo"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -661,7 +661,7 @@
 	      ></p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Bar" open="open"
+	  ><details id="i:Bar"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1197,7 +1197,7 @@
 	      ></p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Baz" open="open"
+	  ><details id="i:Baz"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1549,7 +1549,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Quux" open="open"
+	  ><details id="i:Quux"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1883,7 +1883,7 @@
 	      ></p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Norf" open="open"
+	  ><details id="i:Norf"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/QuasiExpr.html b/html-test/ref/QuasiExpr.html
index ccec6856e2..f1c50e14d8 100644
--- a/html-test/ref/QuasiExpr.html
+++ b/html-test/ref/QuasiExpr.html
@@ -101,7 +101,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Expr" open="open"
+	  ><details id="i:Expr"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -217,7 +217,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:BinOp" open="open"
+	  ><details id="i:BinOp"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/SpuriousSuperclassConstraints.html b/html-test/ref/SpuriousSuperclassConstraints.html
index 53421ff558..0cf8d25506 100644
--- a/html-test/ref/SpuriousSuperclassConstraints.html
+++ b/html-test/ref/SpuriousSuperclassConstraints.html
@@ -81,7 +81,7 @@
 	    >#</a
 	    ></p
 	  ><div class="subs instances"
-	  ><details id="i:SomeType" open="open"
+	  ><details id="i:SomeType"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/Test.html b/html-test/ref/Test.html
index 4bcd25080a..6dec75ab62 100644
--- a/html-test/ref/Test.html
+++ b/html-test/ref/Test.html
@@ -1563,7 +1563,7 @@
 	      ></p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:D" open="open"
+	  ><details id="i:D"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/TypeFamilies.html b/html-test/ref/TypeFamilies.html
index dcb5a92a42..b8bb6a00a8 100644
--- a/html-test/ref/TypeFamilies.html
+++ b/html-test/ref/TypeFamilies.html
@@ -215,7 +215,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:X" open="open"
+	  ><details id="i:X"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -663,7 +663,7 @@
 	    >Doc for: data Y</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Y" open="open"
+	  ><details id="i:Y"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1035,7 +1035,7 @@
 	      ></table
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Z" open="open"
+	  ><details id="i:Z"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1117,7 +1117,7 @@
 	    >Doc for: class Test a</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Test" open="open"
+	  ><details id="i:Test"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1195,7 +1195,7 @@
 	    >Doc for: type family Foo a</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Foo" open="open"
+	  ><details id="i:Foo"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1299,7 +1299,7 @@
 	    >Doc for: data family Bat a</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Bat" open="open"
+	  ><details id="i:Bat"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1523,7 +1523,7 @@
 	      ></div
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Assoc" open="open"
+	  ><details id="i:Assoc"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1705,7 +1705,7 @@
 	    >#</a
 	    ></p
 	  ><div class="subs instances"
-	  ><details id="i:-60--62-" open="open"
+	  ><details id="i:-60--62-"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -1845,7 +1845,7 @@
 	    >#</a
 	    ></p
 	  ><div class="subs instances"
-	  ><details id="i:-62--60-" open="open"
+	  ><details id="i:-62--60-"
 	    ><summary
 	      >Instances</summary
 	      ><table
diff --git a/html-test/ref/TypeFamilies2.html b/html-test/ref/TypeFamilies2.html
index 84e7df3692..bb386d186c 100644
--- a/html-test/ref/TypeFamilies2.html
+++ b/html-test/ref/TypeFamilies2.html
@@ -81,7 +81,7 @@
 	    >Exported type</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:W" open="open"
+	  ><details id="i:W"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -175,7 +175,7 @@
 	    >Exported type family</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Foo" open="open"
+	  ><details id="i:Foo"
 	    ><summary
 	      >Instances</summary
 	      ><table
@@ -267,7 +267,7 @@
 	    >Exported data family</p
 	    ></div
 	  ><div class="subs instances"
-	  ><details id="i:Bar" open="open"
+	  ><details id="i:Bar"
 	    ><summary
 	      >Instances</summary
 	      ><table