diff --git a/caps/BasePrincipal.cpp b/caps/BasePrincipal.cpp
index 69650396ff7f..e7fd751b9ef6 100644
--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -29,8 +29,6 @@ using dom::URLParams;
 void
 OriginAttributes::CreateSuffix(nsACString& aStr) const
 {
-  MOZ_RELEASE_ASSERT(mAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID);
-
   UniquePtr<URLParams> params(new URLParams());
   nsAutoString value;
 
@@ -84,10 +82,6 @@ public:
         return false;
       }
 
-      if (mOriginAttributes->mAppId == nsIScriptSecurityManager::UNKNOWN_APP_ID) {
-        return false;
-      }
-
       return true;
     }
 
@@ -173,14 +167,6 @@ BasePrincipal::GetOrigin(nsACString& aOrigin)
   nsresult rv = GetOriginInternal(aOrigin);
   NS_ENSURE_SUCCESS(rv, rv);
 
-  // OriginAttributes::CreateSuffix asserts against UNKNOWN_APP_ID. It's trivial
-  // to trigger this getter from script on such a principal, so we handle it
-  // here at the API entry point.
-  if (mOriginAttributes.mAppId == nsIScriptSecurityManager::UNKNOWN_APP_ID) {
-    NS_WARNING("Refusing to provide canonical origin string to principal with UNKNOWN_APP_ID");
-    return NS_ERROR_FAILURE;
-  }
-
   nsAutoCString suffix;
   mOriginAttributes.CreateSuffix(suffix);
   aOrigin.Append(suffix);
@@ -276,8 +262,6 @@ BasePrincipal::GetIsNullPrincipal(bool* aIsNullPrincipal)
 NS_IMETHODIMP
 BasePrincipal::GetJarPrefix(nsACString& aJarPrefix)
 {
-  MOZ_ASSERT(AppId() != nsIScriptSecurityManager::UNKNOWN_APP_ID);
-
   mozilla::GetJarPrefix(mOriginAttributes.mAppId, mOriginAttributes.mInBrowser, aJarPrefix);
   return NS_OK;
 }
diff --git a/caps/nsNullPrincipal.cpp b/caps/nsNullPrincipal.cpp
index 37c82bd3593d..37ec76f54531 100644
--- a/caps/nsNullPrincipal.cpp
+++ b/caps/nsNullPrincipal.cpp
@@ -57,7 +57,6 @@ nsresult
 nsNullPrincipal::Init(const OriginAttributes& aOriginAttributes)
 {
   mOriginAttributes = aOriginAttributes;
-  MOZ_ASSERT(AppId() != nsIScriptSecurityManager::UNKNOWN_APP_ID);
 
   mURI = nsNullPrincipalURI::Create();
   NS_ENSURE_TRUE(mURI, NS_ERROR_NOT_AVAILABLE);
@@ -173,9 +172,6 @@ nsNullPrincipal::Read(nsIObjectInputStream* aStream)
 NS_IMETHODIMP
 nsNullPrincipal::Write(nsIObjectOutputStream* aStream)
 {
-  NS_ENSURE_TRUE(mOriginAttributes.mAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID,
-                 NS_ERROR_INVALID_ARG);
-
   nsAutoCString suffix;
   OriginAttributesRef().CreateSuffix(suffix);
 
diff --git a/caps/nsPrincipal.cpp b/caps/nsPrincipal.cpp
index a8b5f400b8a1..c9b8b1de396a 100644
--- a/caps/nsPrincipal.cpp
+++ b/caps/nsPrincipal.cpp
@@ -446,9 +446,6 @@ NS_IMETHODIMP
 nsPrincipal::Write(nsIObjectOutputStream* aStream)
 {
   NS_ENSURE_STATE(mCodebase);
-  NS_ENSURE_TRUE(mOriginAttributes.mAppId != nsIScriptSecurityManager::UNKNOWN_APP_ID,
-                 NS_ERROR_INVALID_ARG);
-
   nsresult rv = NS_WriteOptionalCompoundObject(aStream, mCodebase, NS_GET_IID(nsIURI),
                                                true);
   if (NS_FAILED(rv)) {
diff --git a/caps/tests/unit/test_origin.js b/caps/tests/unit/test_origin.js
index 97c2901adc91..837c6ebd64fc 100644
--- a/caps/tests/unit/test_origin.js
+++ b/caps/tests/unit/test_origin.js
@@ -99,11 +99,7 @@ function run_test() {
   checkOriginAttributes(exampleOrg_addon, { addonId: "dummy" }, '^addonId=dummy');
   do_check_eq(exampleOrg_addon.origin, 'http://example.org^addonId=dummy');
 
-  // Make sure that we refuse to create .origin for principals with UNKNOWN_APP_ID.
-  var simplePrin = ssm.getSimpleCodebasePrincipal(makeURI('http://example.com'));
-  try { simplePrin.origin; do_check_true(false); } catch (e) { do_check_true(true); }
-
-  // Make sure we don't crash when serializing them either.
+  // Make sure we don't crash when serializing principals with UNKNOWN_APP_ID.
   try {
     let binaryStream = Cc["@mozilla.org/binaryoutputstream;1"].
                        createInstance(Ci.nsIObjectOutputStream);