diff --git a/crypto/signature_creator_mac.cc b/crypto/signature_creator_mac.cc
index 544c9fb..c31459f 100644
--- a/crypto/signature_creator_mac.cc
+++ b/crypto/signature_creator_mac.cc
@@ -37,7 +37,7 @@
   return result.release();
 }
 
-SignatureCreator::SignatureCreator() : sig_handle_(0) {
+SignatureCreator::SignatureCreator() : key_(NULL), sig_handle_(0) {
   EnsureCSSMInit();
 }