--- a/layout/style/nsLayoutStylesheetCache.cpp
+++ b/layout/style/nsLayoutStylesheetCache.cpp
@@ -741,18 +741,19 @@ AnnotateCrashReport(nsIURI* aURI)
         }
       }
       delete find;
     }
   } else {
     annotation.AppendLiteral("No GRE omnijar\n");
   }
 
-  CrashReporter::AnnotateCrashReport(NS_LITERAL_CSTRING("SheetLoadFailure"),
-                                     NS_ConvertUTF16toUTF8(annotation));
+  CrashReporter::AnnotateCrashReport(
+    CrashReporter::Annotation::SheetLoadFailure,
+    NS_ConvertUTF16toUTF8(annotation));
 }
 
 static void
 ErrorLoadingSheet(nsIURI* aURI, const char* aMsg, FailureAction aFailureAction)
 {
   nsPrintfCString errorMessage("%s loading built-in stylesheet '%s'",
                                aMsg,
                                aURI ? aURI->GetSpecOrDefault().get() : "");

--- a/toolkit/crashreporter/CrashAnnotations.yaml
+++ b/toolkit/crashreporter/CrashAnnotations.yaml
@@ -509,16 +509,22 @@ SecondsSinceLastCrash:
   type: string
   ping: true
 
 ServerURL:
   description: >
     URL used to post the crash report.
   type: string
 
+SheetLoadFailure:
+  description: >
+    Set when failing to load a built-in style sheet. This can contain a
+    potentially very large amount of diagnostic information.
+  type: string
+
 StartupTime:
   description: >
     The time when Firefox was launched expressed in seconds since the Epoch.
   type: integer
   content: false
 
 StatFailure:
   description: >