--- a/content/base/src/nsStyleLinkElement.cpp
+++ b/content/base/src/nsStyleLinkElement.cpp
@@ -10,16 +10,17 @@
  * stylesheets (<style>, <link>, processing instructions, etc).
  */
 
 #include "nsStyleLinkElement.h"
 
 #include "mozilla/css/Loader.h"
 #include "mozilla/dom/Element.h"
 #include "mozilla/dom/ShadowRoot.h"
+#include "mozilla/Preferences.h"
 #include "nsCSSStyleSheet.h"
 #include "nsIContent.h"
 #include "nsIDocument.h"
 #include "nsIDOMComment.h"
 #include "nsIDOMNode.h"
 #include "nsIDOMStyleSheet.h"
 #include "nsNetUtil.h"
 #include "nsUnicharUtils.h"
@@ -115,29 +116,44 @@ nsStyleLinkElement::OverrideBaseURI(nsIU
 }
 
 /* virtual */ void
 nsStyleLinkElement::SetLineNumber(uint32_t aLineNumber)
 {
   mLineNumber = aLineNumber;
 }
 
+/* static */ bool
+nsStyleLinkElement::IsImportEnabled()
+{
+  static bool sAdded = false;
+  static bool sImportEnabled;
+  if (!sAdded) {
+    // This part runs only once because of the static flag.
+    Preferences::AddBoolVarCache(&sImportEnabled,
+                                 "dom.webcomponents.enabled",
+                                 false);
+    sAdded = true;
+  }
+  return sImportEnabled;
+}
+
 static uint32_t ToLinkMask(const nsAString& aLink)
 { 
   if (aLink.EqualsLiteral("prefetch"))
     return nsStyleLinkElement::ePREFETCH;
   else if (aLink.EqualsLiteral("dns-prefetch"))
     return nsStyleLinkElement::eDNS_PREFETCH;
   else if (aLink.EqualsLiteral("stylesheet"))
     return nsStyleLinkElement::eSTYLESHEET;
   else if (aLink.EqualsLiteral("next"))
     return nsStyleLinkElement::eNEXT;
   else if (aLink.EqualsLiteral("alternate"))
     return nsStyleLinkElement::eALTERNATE;
-  else if (aLink.EqualsLiteral("import"))
+  else if (aLink.EqualsLiteral("import") && nsStyleLinkElement::IsImportEnabled())
     return nsStyleLinkElement::eHTMLIMPORT;
   else 
     return 0;
 }
 
 uint32_t nsStyleLinkElement::ParseLinkTypes(const nsAString& aTypes)
 {
   uint32_t linkMask = 0;

--- a/content/base/src/nsStyleLinkElement.h
+++ b/content/base/src/nsStyleLinkElement.h
@@ -59,16 +59,18 @@ public:
     eNEXT =         0x00000008,
     eALTERNATE =    0x00000010,
     eHTMLIMPORT =   0x00000020
   };
 
   // The return value is a bitwise or of 0 or more RelValues
   static uint32_t ParseLinkTypes(const nsAString& aTypes);
 
+  static bool IsImportEnabled();
+  
   void UpdateStyleSheetInternal()
   {
     UpdateStyleSheetInternal(nullptr, nullptr);
   }
 protected:
   /**
    * @param aOldDocument should be non-null only if we're updating because we
    *                     removed the node from the document.

--- a/content/html/content/src/HTMLLinkElement.cpp
+++ b/content/html/content/src/HTMLLinkElement.cpp
@@ -284,17 +284,17 @@ HTMLLinkElement::UpdateImport()
   }
 
   nsCOMPtr<nsIURI> uri = GetHrefURI();
   if (!uri) {
     mImportLoader = nullptr;
     return;
   }
 
-  if (!Preferences::GetBool("dom.webcomponents.enabled")) {
+  if (!nsStyleLinkElement::IsImportEnabled()) {
     // For now imports are hidden behind a pref...
     return;
   }
 
   nsRefPtr<ImportManager> manager = doc->ImportManager();
   MOZ_ASSERT(manager, "ImportManager should be created lazily when needed");
 
   {