diff --git a/content/base/src/nsDocument.cpp b/content/base/src/nsDocument.cpp
index 464c1474350..8f6bdf95f2b 100644
--- a/content/base/src/nsDocument.cpp
+++ b/content/base/src/nsDocument.cpp
@@ -3583,14 +3583,6 @@ nsDocument::GetStyleSheetAt(int32_t aIndex) const
 int32_t
 nsDocument::GetIndexOfStyleSheet(nsIStyleSheet* aSheet) const
 {
-  if (mAdditionalSheets[eUserSheet].IndexOf(aSheet) >= 0 ||
-      mAdditionalSheets[eAgentSheet].IndexOf(aSheet) >= 0 ) {
-    // Returning INT32_MAX to make sure that additional sheets are
-    // in the style set of the PresShell will be always after the
-    // document sheets (even if document sheets are added dynamically).
-    return INT32_MAX;
-  }
-
   return mStyleSheets.IndexOf(aSheet);
 }