diff --git a/layout/style/nsRuleNode.h b/layout/style/nsRuleNode.h
index d87cda72a21..7398fa2fc0e 100644
--- a/layout/style/nsRuleNode.h
+++ b/layout/style/nsRuleNode.h
@@ -55,7 +55,7 @@ struct nsInheritedStyleData
     return aContext->AllocateFromShell(sz);
   }
 
-  void DestroyStructs(uint32_t aBits, nsPresContext* aContext) {
+  void DestroyStructs(uint64_t aBits, nsPresContext* aContext) {
 #define STYLE_STRUCT_INHERITED(name, checkdata_cb) \
     void *name##Data = mStyleStructs[eStyleStruct_##name]; \
     if (name##Data && !(aBits & NS_STYLE_INHERIT_BIT(name))) \
@@ -68,7 +68,7 @@ struct nsInheritedStyleData
 #undef STYLE_STRUCT_RESET
   }
 
-  void Destroy(uint32_t aBits, nsPresContext* aContext) {
+  void Destroy(uint64_t aBits, nsPresContext* aContext) {
     DestroyStructs(aBits, aContext);
     aContext->FreeToShell(sizeof(nsInheritedStyleData), this);
   }
@@ -100,7 +100,7 @@ struct nsResetStyleData
     return aContext->AllocateFromShell(sz);
   }
 
-  void Destroy(uint32_t aBits, nsPresContext* aContext) {
+  void Destroy(uint64_t aBits, nsPresContext* aContext) {
 #define STYLE_STRUCT_RESET(name, checkdata_cb) \
     void *name##Data = mStyleStructs[eStyleStruct_##name]; \
     if (name##Data && !(aBits & NS_STYLE_INHERIT_BIT(name))) \
@@ -178,7 +178,7 @@ struct nsCachedStyleData
   #undef STYLE_STRUCT_RESET
   #undef STYLE_STRUCT_INHERITED
 
-  void Destroy(uint32_t aBits, nsPresContext* aContext) {
+  void Destroy(uint64_t aBits, nsPresContext* aContext) {
     if (mResetData)
       mResetData->Destroy(aBits, aContext);
     if (mInheritedData)
diff --git a/layout/style/nsStyleContext.cpp b/layout/style/nsStyleContext.cpp
index df8bc327675..ed1ef013476 100644
--- a/layout/style/nsStyleContext.cpp
+++ b/layout/style/nsStyleContext.cpp
@@ -43,14 +43,14 @@ nsStyleContext::nsStyleContext(nsStyleContext* aParent,
     mRuleNode(aRuleNode),
     mAllocations(nullptr),
     mCachedResetData(nullptr),
-    mBits(((uint32_t)aPseudoType) << NS_STYLE_CONTEXT_TYPE_SHIFT),
+    mBits(((uint64_t)aPseudoType) << NS_STYLE_CONTEXT_TYPE_SHIFT),
     mRefCnt(0)
 {
   // This check has to be done "backward", because if it were written the
   // more natural way it wouldn't fail even when it needed to.
-  static_assert((UINT32_MAX >> NS_STYLE_CONTEXT_TYPE_SHIFT) >=
+  static_assert((UINT64_MAX >> NS_STYLE_CONTEXT_TYPE_SHIFT) >=
                 nsCSSPseudoElements::ePseudo_MAX,
-                "pseudo element bits no longer fit in a uint32_t");
+                "pseudo element bits no longer fit in a uint64_t");
   MOZ_ASSERT(aRuleNode);
 
   mNextSibling = this;
@@ -262,7 +262,7 @@ nsStyleContext::GetUniqueStyleData(const nsStyleStructID& aSID)
   }
 
   SetStyle(aSID, result);
-  mBits &= ~nsCachedStyleData::GetBitForSID(aSID);
+  mBits &= ~static_cast<uint64_t>(nsCachedStyleData::GetBitForSID(aSID));
 
   return result;
 }
diff --git a/layout/style/nsStyleContext.h b/layout/style/nsStyleContext.h
index da20c04f895..d0b94ee61c5 100644
--- a/layout/style/nsStyleContext.h
+++ b/layout/style/nsStyleContext.h
@@ -211,7 +211,7 @@ public:
   #undef STYLE_STRUCT_INHERITED
 
   nsRuleNode* RuleNode() { return mRuleNode; }
-  void AddStyleBit(const uint32_t& aBit) { mBits |= aBit; }
+  void AddStyleBit(const uint64_t& aBit) { mBits |= aBit; }
 
   /*
    * Mark this style context's rule node (and its ancestors) to prevent
@@ -430,7 +430,7 @@ protected:
   // sometimes allocate the mCachedResetData.
   nsResetStyleData*       mCachedResetData; // Cached reset style data.
   nsInheritedStyleData    mCachedInheritedData; // Cached inherited style data
-  uint32_t                mBits; // Which structs are inherited from the
+  uint64_t                mBits; // Which structs are inherited from the
                                  // parent context or owned by mRuleNode.
   uint32_t                mRefCnt;
 };
diff --git a/layout/style/nsStyleStructFwd.h b/layout/style/nsStyleStructFwd.h
index d6e845da94d..ee5087358e5 100644
--- a/layout/style/nsStyleStructFwd.h
+++ b/layout/style/nsStyleStructFwd.h
@@ -62,6 +62,6 @@ eStyleStruct_BackendOnly = nsStyleStructID_Length
 };
 
 // A bit corresponding to each struct ID
-#define NS_STYLE_INHERIT_BIT(sid_)        (1 << int32_t(eStyleStruct_##sid_))
+#define NS_STYLE_INHERIT_BIT(sid_)        (1 << uint64_t(eStyleStruct_##sid_))
 
 #endif /* nsStyleStructFwd_h_ */