--- a/security/manager/ssl/nsCryptoHash.cpp
+++ b/security/manager/ssl/nsCryptoHash.cpp
@@ -264,33 +264,30 @@ nsCryptoHMAC::Init(uint32_t aAlgorithm, 
   }
 
   if (mHMACContext)
   {
     PK11_DestroyContext(mHMACContext, true);
     mHMACContext = nullptr;
   }
 
-  CK_MECHANISM_TYPE HMACMechType;
-  switch (aAlgorithm)
-  {
-  case nsCryptoHMAC::MD2:
-    HMACMechType = CKM_MD2_HMAC; break;
-  case nsCryptoHMAC::MD5:
-    HMACMechType = CKM_MD5_HMAC; break;
-  case nsCryptoHMAC::SHA1:
-    HMACMechType = CKM_SHA_1_HMAC; break;
-  case nsCryptoHMAC::SHA256:
-    HMACMechType = CKM_SHA256_HMAC; break;
-  case nsCryptoHMAC::SHA384:
-    HMACMechType = CKM_SHA384_HMAC; break;
-  case nsCryptoHMAC::SHA512:
-    HMACMechType = CKM_SHA512_HMAC; break;
-  default:
-    return NS_ERROR_INVALID_ARG;
+  CK_MECHANISM_TYPE mechType;
+  switch (aAlgorithm) {
+    case nsICryptoHMAC::MD5:
+      mechType = CKM_MD5_HMAC; break;
+    case nsICryptoHMAC::SHA1:
+      mechType = CKM_SHA_1_HMAC; break;
+    case nsICryptoHMAC::SHA256:
+      mechType = CKM_SHA256_HMAC; break;
+    case nsICryptoHMAC::SHA384:
+      mechType = CKM_SHA384_HMAC; break;
+    case nsICryptoHMAC::SHA512:
+      mechType = CKM_SHA512_HMAC; break;
+    default:
+      return NS_ERROR_INVALID_ARG;
   }
 
   NS_ENSURE_ARG_POINTER(aKeyObject);
 
   nsresult rv;
 
   int16_t keyType;
   rv = aKeyObject->GetType(&keyType);
@@ -301,18 +298,17 @@ nsCryptoHMAC::Init(uint32_t aAlgorithm, 
   PK11SymKey* key;
   // GetKeyObj doesn't addref the key
   rv = aKeyObject->GetKeyObj(&key);
   NS_ENSURE_SUCCESS(rv, rv);
 
   SECItem rawData;
   rawData.data = 0;
   rawData.len = 0;
-  mHMACContext = PK11_CreateContextBySymKey(
-      HMACMechType, CKA_SIGN, key, &rawData);
+  mHMACContext = PK11_CreateContextBySymKey(mechType, CKA_SIGN, key, &rawData);
   NS_ENSURE_TRUE(mHMACContext, NS_ERROR_FAILURE);
 
   SECStatus ss = PK11_DigestBegin(mHMACContext);
   NS_ENSURE_TRUE(ss == SECSuccess, NS_ERROR_FAILURE);
 
   return NS_OK;
 }
 

--- a/security/manager/ssl/nsICryptoHMAC.idl
+++ b/security/manager/ssl/nsICryptoHMAC.idl
@@ -10,23 +10,22 @@ interface nsIKeyObject;
  * nsICryptoHMAC
  * This interface provides HMAC signature algorithms.
  */
 
 [scriptable, uuid(8FEB4C7C-1641-4a7b-BC6D-1964E2099497)]
 interface nsICryptoHMAC : nsISupports
 {
     /**
-     * Hashing Algorithms.  These values are to be used by the
-     * |init| method to indicate which hashing function to
-     * use.  These values map onto the values defined in
-     * mozilla/security/nss/lib/softoken/pkcs11t.h and are 
-     * switched to CKM_*_HMAC constant.
+     * Hashing Algorithms. These values are to be used by the |init| method to
+     * indicate which hashing function to use. These values map onto the values
+     * defined in mozilla/security/nss/lib/softoken/pkcs11t.h and are switched
+     * to a CKM_*_HMAC constant.
      */
-    const short MD2    = 1;
+    // 1 used to mean MD2.
     const short MD5    = 2;
     const short SHA1   = 3;
     const short SHA256 = 4;
     const short SHA384 = 5;
     const short SHA512 = 6;
 
     /**
      * Initialize the hashing object. This method may be