--- a/dom/base/DirectionalityUtils.cpp
+++ b/dom/base/DirectionalityUtils.cpp
@@ -281,22 +281,24 @@ GetDirectionFromChar(uint32_t ch)
     case eCharType_LeftToRight:
       return eDir_LTR;
 
     default:
       return eDir_NotSet;
   }
 }
 
-inline static bool NodeAffectsDirAutoAncestor(nsINode* aTextNode)
+inline static bool
+NodeAffectsDirAutoAncestor(nsINode* aTextNode)
 {
   Element* parent = aTextNode->GetParentElement();
   return (parent &&
           !DoesNotParticipateInAutoDirection(parent) &&
-          parent->NodeOrAncestorHasDirAuto());
+          parent->NodeOrAncestorHasDirAuto() &&
+          !aTextNode->IsInAnonymousSubtree());
 }
 
 Directionality
 GetDirectionFromText(const char16_t* aText, const uint32_t aLength,
                      uint32_t* aFirstStrong)
 {
   const char16_t* start = aText;
   const char16_t* end = aText + aLength;

new file mode 100644
--- /dev/null
+++ b/dom/base/crashtests/1377826.html
@@ -0,0 +1,5 @@
+<li id='a' dir='auto'>
+<select>
+<option dir='rtl'>
+&#x8C3;
+</html>

--- a/dom/base/crashtests/crashtests.list
+++ b/dom/base/crashtests/crashtests.list
@@ -209,12 +209,13 @@ pref(dom.IntersectionObserver.enabled,tr
 pref(dom.IntersectionObserver.enabled,true) load 1326194-2.html
 pref(dom.IntersectionObserver.enabled,true) load 1332939.html
 pref(dom.webcomponents.enabled,true) load 1341693.html
 pref(dom.IntersectionObserver.enabled,true) load 1353529.xul
 pref(dom.IntersectionObserver.enabled,true) load 1369363.xul
 load 1370072.html
 pref(clipboard.autocopy,true) load 1370737.html
 pref(dom.IntersectionObserver.enabled,true) load 1370968.html
+load 1377826.html
 load structured_clone_container_throws.html
 HTTP(..) load xhr_abortinprogress.html
 load xhr_empty_datauri.html
 load xhr_html_nullresponse.html