diff --git a/caps/BasePrincipal.cpp b/caps/BasePrincipal.cpp
index 0847a45d8843..a0684ecec2e8 100644
--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -30,7 +30,8 @@ namespace mozilla {
 
 BasePrincipal::BasePrincipal(PrincipalKind aKind)
   : mKind(aKind)
-  , mDomainSet(false)
+  , mHasExplicitDomain(false)
+  , mInitialized(false)
 {}
 
 BasePrincipal::~BasePrincipal()
@@ -39,6 +40,8 @@ BasePrincipal::~BasePrincipal()
 NS_IMETHODIMP
 BasePrincipal::GetOrigin(nsACString& aOrigin)
 {
+  MOZ_ASSERT(mInitialized);
+
   nsresult rv = GetOriginNoSuffix(aOrigin);
   NS_ENSURE_SUCCESS(rv, rv);
 
@@ -52,6 +55,8 @@ BasePrincipal::GetOrigin(nsACString& aOrigin)
 NS_IMETHODIMP
 BasePrincipal::GetOriginNoSuffix(nsACString& aOrigin)
 {
+  MOZ_ASSERT(mInitialized);
+
   if (mOriginNoSuffix) {
     return mOriginNoSuffix->ToUTF8String(aOrigin);
   }
@@ -456,8 +461,11 @@ BasePrincipal::AddonAllowsLoad(nsIURI* aURI, bool aExplicit /* = false */)
 }
 
 void
-BasePrincipal::FinishInit()
+BasePrincipal::FinishInit(const OriginAttributes& aOriginAttributes)
 {
+  mInitialized = true;
+  mOriginAttributes = aOriginAttributes;
+
   // First compute the origin suffix since it's infallible.
   nsAutoCString originSuffix;
   mOriginAttributes.CreateSuffix(originSuffix);
diff --git a/caps/BasePrincipal.h b/caps/BasePrincipal.h
index 2108e4490c3f..2c756521354e 100644
--- a/caps/BasePrincipal.h
+++ b/caps/BasePrincipal.h
@@ -115,18 +115,27 @@ protected:
   virtual bool MayLoadInternal(nsIURI* aURI) = 0;
   friend class ::ExpandedPrincipal;
 
+  void
+  SetHasExplicitDomain()
+  {
+    mHasExplicitDomain = true;
+  }
+
   // This function should be called as the last step of the initialization of the
   // principal objects.  It's typically called as the last step from the Init()
   // method of the child classes.
-  void FinishInit();
+  void FinishInit(const OriginAttributes& aOriginAttributes);
 
   nsCOMPtr<nsIContentSecurityPolicy> mCSP;
   nsCOMPtr<nsIContentSecurityPolicy> mPreloadCSP;
   nsCOMPtr<nsIAtom> mOriginNoSuffix;
   nsCOMPtr<nsIAtom> mOriginSuffix;
+
+private:
   OriginAttributes mOriginAttributes;
   PrincipalKind mKind;
-  bool mDomainSet;
+  bool mHasExplicitDomain;
+  bool mInitialized;
 };
 
 inline bool
@@ -169,7 +178,7 @@ BasePrincipal::FastEqualsConsideringDomain(nsIPrincipal* aOther)
   // If neither of the principals have document.domain set, we use the fast path
   // in Equals().  Otherwise, we fall back to the slow path below.
   auto other = Cast(aOther);
-  if (!mDomainSet && !other->mDomainSet) {
+  if (!mHasExplicitDomain && !other->mHasExplicitDomain) {
     return FastEquals(aOther);
   }
 
@@ -205,7 +214,7 @@ BasePrincipal::FastSubsumesConsideringDomain(nsIPrincipal* aOther)
   // If neither of the principals have document.domain set, we hand off to
   // FastSubsumes() which has fast paths for some special cases. Otherwise, we fall
   // back to the slow path below.
-  if (!mDomainSet && !Cast(aOther)->mDomainSet) {
+  if (!mHasExplicitDomain && !Cast(aOther)->mHasExplicitDomain) {
     return FastSubsumes(aOther);
   }
 
diff --git a/caps/ContentPrincipal.cpp b/caps/ContentPrincipal.cpp
index 51447d46c85a..bd2cca8b7c9e 100644
--- a/caps/ContentPrincipal.cpp
+++ b/caps/ContentPrincipal.cpp
@@ -82,7 +82,6 @@ ContentPrincipal::ContentPrincipal()
   : BasePrincipal(eCodebasePrincipal)
   , mCodebaseImmutable(false)
   , mDomainImmutable(false)
-  , mInitialized(false)
 {
 }
 
@@ -98,11 +97,8 @@ nsresult
 ContentPrincipal::Init(nsIURI *aCodebase,
                        const OriginAttributes& aOriginAttributes)
 {
-  NS_ENSURE_STATE(!mInitialized);
   NS_ENSURE_ARG(aCodebase);
 
-  mInitialized = true;
-
   // Assert that the URI we get here isn't any of the schemes that we know we
   // should not get here.  These schemes always either inherit their principal
   // or fall back to a null principal.  These are schemes which return
@@ -118,9 +114,8 @@ ContentPrincipal::Init(nsIURI *aCodebase,
 
   mCodebase = NS_TryToMakeImmutable(aCodebase);
   mCodebaseImmutable = URIIsImmutable(mCodebase);
-  mOriginAttributes = aOriginAttributes;
 
-  FinishInit();
+  FinishInit(aOriginAttributes);
 
   return NS_OK;
 }
@@ -372,7 +367,7 @@ ContentPrincipal::SetDomain(nsIURI* aDomain)
 {
   mDomain = NS_TryToMakeImmutable(aDomain);
   mDomainImmutable = URIIsImmutable(mDomain);
-  mDomainSet = true;
+  SetHasExplicitDomain();
 
   // Recompute all wrappers between compartments using this principal and other
   // non-chrome compartments.
diff --git a/caps/ContentPrincipal.h b/caps/ContentPrincipal.h
index 2e3be1cf7e94..a52445fa8567 100644
--- a/caps/ContentPrincipal.h
+++ b/caps/ContentPrincipal.h
@@ -47,7 +47,6 @@ public:
   // If mCodebaseImmutable is true, mCodebase is non-null and immutable
   bool mCodebaseImmutable;
   bool mDomainImmutable;
-  bool mInitialized;
 
 protected:
   virtual ~ContentPrincipal();
diff --git a/caps/ExpandedPrincipal.cpp b/caps/ExpandedPrincipal.cpp
index 5b186684ee6d..3257b5f23359 100644
--- a/caps/ExpandedPrincipal.cpp
+++ b/caps/ExpandedPrincipal.cpp
@@ -43,8 +43,7 @@ struct OriginComparator
   }
 };
 
-ExpandedPrincipal::ExpandedPrincipal(nsTArray<nsCOMPtr<nsIPrincipal>> &aWhiteList,
-                                     const OriginAttributes& aAttrs)
+ExpandedPrincipal::ExpandedPrincipal(nsTArray<nsCOMPtr<nsIPrincipal>> &aWhiteList)
   : BasePrincipal(eExpandedPrincipal)
 {
   // We force the principals to be sorted by origin so that ExpandedPrincipal
@@ -53,7 +52,6 @@ ExpandedPrincipal::ExpandedPrincipal(nsTArray<nsCOMPtr<nsIPrincipal>> &aWhiteLis
   for (size_t i = 0; i < aWhiteList.Length(); ++i) {
     mPrincipals.InsertElementSorted(aWhiteList[i], c);
   }
-  mOriginAttributes = aAttrs;
 }
 
 ExpandedPrincipal::~ExpandedPrincipal()
@@ -63,8 +61,8 @@ already_AddRefed<ExpandedPrincipal>
 ExpandedPrincipal::Create(nsTArray<nsCOMPtr<nsIPrincipal>>& aWhiteList,
                           const OriginAttributes& aAttrs)
 {
-  RefPtr<ExpandedPrincipal> ep = new ExpandedPrincipal(aWhiteList, aAttrs);
-  ep->FinishInit();
+  RefPtr<ExpandedPrincipal> ep = new ExpandedPrincipal(aWhiteList);
+  ep->FinishInit(aAttrs);
   return ep.forget();
 }
 
diff --git a/caps/ExpandedPrincipal.h b/caps/ExpandedPrincipal.h
index 416f0ea80f45..c296326224fc 100644
--- a/caps/ExpandedPrincipal.h
+++ b/caps/ExpandedPrincipal.h
@@ -15,9 +15,6 @@
 class ExpandedPrincipal : public nsIExpandedPrincipal
                         , public mozilla::BasePrincipal
 {
-  ExpandedPrincipal(nsTArray<nsCOMPtr<nsIPrincipal>> &aWhiteList,
-                    const mozilla::OriginAttributes& aAttrs);
-
 public:
   static already_AddRefed<ExpandedPrincipal>
   Create(nsTArray<nsCOMPtr<nsIPrincipal>>& aWhiteList,
@@ -40,6 +37,8 @@ public:
   nsresult GetOriginNoSuffixInternal(nsACString& aOrigin) override;
 
 protected:
+  explicit ExpandedPrincipal(nsTArray<nsCOMPtr<nsIPrincipal>> &aWhiteList);
+
   virtual ~ExpandedPrincipal();
 
   bool SubsumesInternal(nsIPrincipal* aOther,
diff --git a/caps/NullPrincipal.cpp b/caps/NullPrincipal.cpp
index 4db8fd7110a0..4b1395c4e9bf 100644
--- a/caps/NullPrincipal.cpp
+++ b/caps/NullPrincipal.cpp
@@ -70,8 +70,6 @@ NullPrincipal::Create(const OriginAttributes& aOriginAttributes, nsIURI* aURI)
 nsresult
 NullPrincipal::Init(const OriginAttributes& aOriginAttributes, nsIURI* aURI)
 {
-  mOriginAttributes = aOriginAttributes;
-
   if (aURI) {
     nsAutoCString scheme;
     nsresult rv = aURI->GetScheme(scheme);
@@ -86,7 +84,7 @@ NullPrincipal::Init(const OriginAttributes& aOriginAttributes, nsIURI* aURI)
     NS_ENSURE_TRUE(mURI, NS_ERROR_NOT_AVAILABLE);
   }
 
-  FinishInit();
+  FinishInit(aOriginAttributes);
 
   return NS_OK;
 }
diff --git a/caps/SystemPrincipal.cpp b/caps/SystemPrincipal.cpp
index 72aff5306f52..8bd14fd890e7 100644
--- a/caps/SystemPrincipal.cpp
+++ b/caps/SystemPrincipal.cpp
@@ -35,7 +35,7 @@ already_AddRefed<SystemPrincipal>
 SystemPrincipal::Create()
 {
   RefPtr<SystemPrincipal> sp = new SystemPrincipal();
-  sp->FinishInit();
+  sp->FinishInit(OriginAttributes());
   return sp.forget();
 }