diff --git a/lib/frames/sasl_frame.js b/lib/frames/sasl_frame.js
index e7dc037..55a8a9e 100644
--- a/lib/frames/sasl_frame.js
+++ b/lib/frames/sasl_frame.js
@@ -105,15 +105,13 @@ module.exports.SaslFrame = SaslFrame;
  */
 function SaslMechanisms(options) {
   SaslMechanisms.super_.call(this);
+  if (options instanceof DescribedType) {
+    return this.fromDescribedType(options);
+  }
+
   if (options) {
-    if (options instanceof DescribedType) {
-      this.mechanisms = (options.value[0] instanceof Array) ?
-          options.value[0].map(function(x) { return x.contents; }) :
-          [options.value[0].contents];
-    } else {
-      this.mechanisms = options instanceof Array ?
-          options : (options.mechanisms || []);
-    }
+    this.mechanisms =
+      (options instanceof Array) ? options : (options.mechanisms || []);
   } else {
     this.mechanisms = [];
   }
@@ -123,7 +121,7 @@ util.inherits(SaslMechanisms, SaslFrame);
 module.exports.SaslMechanisms = SaslMechanisms;
 
 SaslMechanisms.prototype.Descriptor = { code: 0x40, name: 'amqp:sasl-mechanisms:list' };
-SaslMechanisms.prototype.toDescribedType = function(b) {
+SaslMechanisms.prototype.toDescribedType = function() {
   if (!this.mechanisms || this.mechanisms.length === 0) {
     this.mechanisms = ['ANONYMOUS'];
   }
@@ -133,7 +131,11 @@ SaslMechanisms.prototype.toDescribedType = function(b) {
   return new DescribedType(SaslMechanisms, value);
 };
 
-
+SaslMechanisms.prototype.fromDescribedType = function(described) {
+  this.mechanisms = (described.value[0] instanceof Array) ?
+      described.value[0].map(function(x) { return x.contents; }) :
+      [ described.value[0].contents ];
+};
 
 /**
  * SASL Init frame, containing the following fields:
@@ -182,16 +184,13 @@ SaslMechanisms.prototype.toDescribedType = function(b) {
 function SaslInit(options) {
   SaslInit.super_.call(this);
   if (options instanceof DescribedType) {
-    this.mechanism = up.onUndef(options, 0, 'ANONYMOUS');
-    if (this.mechanism instanceof AMQPSymbol) this.mechanism = this.mechanism.contents;
-    this.initialResponse = up.get(options, 1);
-    this.hostname = up.get(options, 2);
-  } else {
-    u.assertArguments(options, ['mechanism']);
-    this.mechanism = u.coerce(options.mechanism, AMQPSymbol);
-    this.initialResponse = options.initialResponse;
-    this.hostname = options.hostname;
+    return this.fromDescribedType(options);
   }
+
+  u.assertArguments(options, ['mechanism']);
+  this.mechanism = u.coerce(options.mechanism, AMQPSymbol);
+  this.initialResponse = options.initialResponse;
+  this.hostname = options.hostname;
 }
 
 util.inherits(SaslInit, SaslFrame);
@@ -206,7 +205,12 @@ SaslInit.prototype.toDescribedType = function() {
   ]);
 };
 
-
+SaslInit.prototype.fromDescribedType = function(described) {
+  this.mechanism = up.onUndef(described, 0, 'ANONYMOUS');
+  if (this.mechanism instanceof AMQPSymbol) this.mechanism = this.mechanism.contents;
+  this.initialResponse = up.get(described, 1);
+  this.hostname = up.get(described, 2);
+};
 
 /**
  * SASL Challenge frame, containing the following field:
@@ -226,8 +230,10 @@ SaslInit.prototype.toDescribedType = function() {
 function SaslChallenge(options) {
   SaslChallenge.super_.call(this);
   if (options instanceof DescribedType) {
-    this.challenge = up.orNull(options, 0);
-  } else if (options instanceof Buffer) {
+    return this.fromDescribedType(options);
+  }
+
+  if (options instanceof Buffer) {
     this.challenge = options;
   } else {
     u.assertArguments(options, ['challenge']);
@@ -243,6 +249,9 @@ SaslChallenge.prototype.toDescribedType = function() {
   return new DescribedType(SaslChallenge, [ this.challenge ]);
 };
 
+SaslChallenge.prototype.fromDescribedType = function(described) {
+  this.challenge = up.orNull(described, 0);
+};
 
 
 /**
@@ -263,8 +272,10 @@ SaslChallenge.prototype.toDescribedType = function() {
 function SaslResponse(options) {
   SaslResponse.super_.call(this);
   if (options instanceof DescribedType) {
-    this.response = up.orNull(options, 0);
-  } else if (options instanceof Buffer) {
+    return this.fromDescribedType(options);
+  }
+
+  if (options instanceof Buffer) {
     this.response = options;
   } else {
     u.assertArguments(options, ['response']);
@@ -280,6 +291,9 @@ SaslResponse.prototype.toDescribedType = function() {
   return new DescribedType(SaslResponse, [ this.response ]);
 };
 
+SaslResponse.prototype.fromDescribedType = function(described) {
+  this.response = up.orNull(described, 0);
+};
 
 
 /**
@@ -329,15 +343,12 @@ SaslResponse.prototype.toDescribedType = function() {
 function SaslOutcome(options) {
   SaslOutcome.super_.call(this);
   if (options instanceof DescribedType) {
-    up.assert(options, 0, 'code');
-    this.code = up.get(options, 0);
-    this.additionalData = up.get(options, 1);
-    this.details = constants.saslOutcomes[this.code];
-  } else {
-    u.assertArguments(options, ['code']);
-    this.code = options.code;
-    this.additionalData = options.additionalData;
+    return this.fromDescribedType(options);
   }
+
+  u.assertArguments(options, ['code']);
+  this.code = options.code;
+  this.additionalData = options.additionalData;
 }
 
 util.inherits(SaslOutcome, SaslFrame);
@@ -350,3 +361,10 @@ SaslOutcome.prototype.toDescribedType = function() {
     u.orNull(this.additionalData)
   ]);
 };
+
+SaslOutcome.prototype.fromDescribedType = function(described) {
+  up.assert(described, 0, 'code');
+  this.code = up.get(described, 0);
+  this.additionalData = up.get(described, 1);
+  this.details = constants.saslOutcomes[this.code];
+};