diff --git a/caps/BasePrincipal.cpp b/caps/BasePrincipal.cpp
index ffe9f420e197..0a963523e728 100644
--- a/caps/BasePrincipal.cpp
+++ b/caps/BasePrincipal.cpp
@@ -423,6 +423,17 @@ BasePrincipal::GetIsExpandedPrincipal(bool* aResult) {
   return NS_OK;
 }
 
+NS_IMETHODIMP
+BasePrincipal::GetAsciiSpec(nsACString& aSpec) {
+  aSpec.Truncate();
+  nsCOMPtr<nsIURI> prinURI;
+  nsresult rv = GetURI(getter_AddRefs(prinURI));
+  if (NS_FAILED(rv) || !prinURI) {
+    return NS_OK;
+  }
+  return prinURI->GetAsciiSpec(aSpec);
+}
+
 NS_IMETHODIMP
 BasePrincipal::GetIsSystemPrincipal(bool* aResult) {
   *aResult = IsSystemPrincipal();
diff --git a/caps/BasePrincipal.h b/caps/BasePrincipal.h
index 0b968157d0a5..c466d01161dd 100644
--- a/caps/BasePrincipal.h
+++ b/caps/BasePrincipal.h
@@ -121,6 +121,7 @@ class BasePrincipal : public nsJSPrincipals {
   NS_IMETHOD GetIsAddonOrExpandedAddonPrincipal(bool* aResult) override;
   NS_IMETHOD GetOriginAttributes(JSContext* aCx,
                                  JS::MutableHandle<JS::Value> aVal) final;
+  NS_IMETHOD GetAsciiSpec(nsACString& aSpec) override;
   NS_IMETHOD GetOriginSuffix(nsACString& aOriginSuffix) final;
   NS_IMETHOD GetIsInIsolatedMozBrowserElement(
       bool* aIsInIsolatedMozBrowserElement) final;
diff --git a/caps/nsIPrincipal.idl b/caps/nsIPrincipal.idl
index f5fef865a9d4..b7d9c2702882 100644
--- a/caps/nsIPrincipal.idl
+++ b/caps/nsIPrincipal.idl
@@ -199,6 +199,16 @@ interface nsIPrincipal : nsISerializable
      */
     readonly attribute ACString origin;
 
+    /**
+      * Returns the ASCII Spec from the Principals URI.
+      * Might return the empty string, e.g. for the case of
+      * a SystemPrincipal or an EpxandedPrincipal.
+      *
+      * WARNING: DO NOT USE FOR SECURITY CHECKS.
+      * just for logging purposes!
+     */
+     readonly attribute ACString AsciiSpec;
+
     /**
     * Checks if the Principal's URI Scheme matches with the parameter
     *
diff --git a/dom/security/FramingChecker.cpp b/dom/security/FramingChecker.cpp
index cd58980e249e..9db201a71bd2 100644
--- a/dom/security/FramingChecker.cpp
+++ b/dom/security/FramingChecker.cpp
@@ -30,15 +30,13 @@ void FramingChecker::ReportError(const char* aMessageTag,
   }
 
   Document* parentDocument = aParentDocShellItem->GetDocument();
-  nsCOMPtr<nsIURI> parentURI;
-  parentDocument->NodePrincipal()->GetURI(getter_AddRefs(parentURI));
   MOZ_ASSERT(!parentDocument->NodePrincipal()->IsSystemPrincipal(),
              "Should not get system principal here.");
 
   // Get the parent URL spec
   nsAutoCString parentSpec;
   nsresult rv;
-  rv = parentURI->GetAsciiSpec(parentSpec);
+  rv = parentDocument->NodePrincipal()->GetAsciiSpec(parentSpec);
   if (NS_FAILED(rv)) {
     return;
   }
diff --git a/dom/security/nsContentSecurityManager.cpp b/dom/security/nsContentSecurityManager.cpp
index c01b236935b4..3b9c0d3e256c 100644
--- a/dom/security/nsContentSecurityManager.cpp
+++ b/dom/security/nsContentSecurityManager.cpp
@@ -629,12 +629,8 @@ static void LogPrincipal(nsIPrincipal* aPrincipal,
                origin.get()));
       return;
     }
-    nsCOMPtr<nsIURI> principalURI;
     nsAutoCString principalSpec;
-    aPrincipal->GetURI(getter_AddRefs(principalURI));
-    if (principalURI) {
-      principalURI->GetSpec(principalSpec);
-    }
+    aPrincipal->GetAsciiSpec(principalSpec);
     MOZ_LOG(sCSMLog, LogLevel::Debug,
             ("  %s: %s\n", NS_ConvertUTF16toUTF8(aPrincipalName).get(),
              principalSpec.get()));
diff --git a/gfx/thebes/gfxUserFontSet.cpp b/gfx/thebes/gfxUserFontSet.cpp
index 6f1567e0e6d4..781ee86b22ea 100644
--- a/gfx/thebes/gfxUserFontSet.cpp
+++ b/gfx/thebes/gfxUserFontSet.cpp
@@ -1374,18 +1374,15 @@ void gfxUserFontSet::UserFontCache::Entry::ReportMemory(
       path.AppendPrintf(", url=%s", spec.get());
     }
     if (mPrincipal) {
-      nsCOMPtr<nsIURI> uri;
-      mPrincipal->get()->GetURI(getter_AddRefs(uri));
-      if (uri) {
-        nsCString spec = uri->GetSpecOrDefault();
-        if (!spec.IsEmpty()) {
-          // Include a clue as to who loaded this resource. (Note
-          // that because of font entry sharing, other pages may now
-          // be using this resource, and the original page may not
-          // even be loaded any longer.)
-          spec.ReplaceChar('/', '\\');
-          path.AppendPrintf(", principal=%s", spec.get());
-        }
+      nsAutoCString spec;
+      mPrincipal->get()->GetAsciiSpec(spec);
+      if (!spec.IsEmpty()) {
+        // Include a clue as to who loaded this resource. (Note
+        // that because of font entry sharing, other pages may now
+        // be using this resource, and the original page may not
+        // even be loaded any longer.)
+        spec.ReplaceChar('/', '\\');
+        path.AppendPrintf(", principal=%s", spec.get());
       }
     }
   }