diff --git a/mailnews/mime/src/mimecms.cpp b/mailnews/mime/src/mimecms.cpp
index 227654bc1f..622e536b97 100644
--- a/mailnews/mime/src/mimecms.cpp
+++ b/mailnews/mime/src/mimecms.cpp
@@ -286,6 +286,7 @@ SignedStatusRunnable::SignedStatusRunnable(
     int32_t aNestingLevel, int32_t aSignatureStatus, nsIX509Cert* aSignerCert,
     const nsCString& aMsgNeckoURL)
     : mozilla::Runnable("SignedStatusRunnable"),
+      mResult(NS_ERROR_UNEXPECTED),
       m_sink(aSink),
       m_nestingLevel(aNestingLevel),
       m_signatureStatus(aSignatureStatus),