diff --git a/src/packet/public_key_encrypted_session_key.js b/src/packet/public_key_encrypted_session_key.js
index f0bdc402..eaa5dacd 100644
--- a/src/packet/public_key_encrypted_session_key.js
+++ b/src/packet/public_key_encrypted_session_key.js
@@ -208,11 +208,14 @@ class PublicKeyEncryptedSessionKeyPacket {
 
     const { sessionKey, sessionKeyAlgorithm } = decodeSessionKey(this.version, this.publicKeyAlgorithm, decryptedData, randomSessionKey);
 
-    // v3 Montgomery curves have cleartext cipher algo
-    if (this.version === 3 && (
-      this.publicKeyAlgorithm !== enums.publicKey.x25519 && this.publicKeyAlgorithm !== enums.publicKey.x448)
-    ) {
-      this.sessionKeyAlgorithm = sessionKeyAlgorithm;
+    if (this.version === 3) {
+      // v3 Montgomery curves have cleartext cipher algo
+      const hasEncryptedAlgo = this.publicKeyAlgorithm !== enums.publicKey.x25519 && this.publicKeyAlgorithm !== enums.publicKey.x448;
+      this.sessionKeyAlgorithm = hasEncryptedAlgo ? sessionKeyAlgorithm : this.sessionKeyAlgorithm;
+
+      if (sessionKey.length !== crypto.getCipherParams(this.sessionKeyAlgorithm).keySize) {
+        throw new Error('Unexpected session key size');
+      }
     }
     this.sessionKey = sessionKey;
   }
diff --git a/src/packet/sym_encrypted_session_key.js b/src/packet/sym_encrypted_session_key.js
index 464be72e..4ea592f9 100644
--- a/src/packet/sym_encrypted_session_key.js
+++ b/src/packet/sym_encrypted_session_key.js
@@ -56,7 +56,7 @@ class SymEncryptedSessionKeyPacket {
      * Algorithm to encrypt the message with
      * @type {enums.symmetric}
      */
-    this.sessionKeyAlgorithm = enums.symmetric.aes256;
+    this.sessionKeyAlgorithm = null;
     /**
      * AEAD mode to encrypt the session key with (if AEAD protection is enabled)
      * @type {enums.aead}
@@ -177,7 +177,11 @@ class SymEncryptedSessionKeyPacket {
 
       this.sessionKeyAlgorithm = enums.write(enums.symmetric, decrypted[0]);
       this.sessionKey = decrypted.subarray(1, decrypted.length);
+      if (this.sessionKey.length !== crypto.getCipherParams(this.sessionKeyAlgorithm).keySize) {
+        throw new Error('Unexpected session key size');
+      }
     } else {
+      // session key size is checked as part of SEIPDv2 decryption, where we know the expected symmetric algo
       this.sessionKey = key;
     }
   }
diff --git a/test/crypto/eax.js b/test/crypto/eax.js
index d5191b37..a18688a2 100644
--- a/test/crypto/eax.js
+++ b/test/crypto/eax.js
@@ -159,7 +159,7 @@ export default () => describe('Symmetric AES-EAX', function() {
     testAESEAX();
   });
 
-  describe('Symmetric AES-EAX (asm.js fallback)', function() {
+  describe('Symmetric AES-EAX (non-native fallback)', function() {
     beforeEach(function () {
       sinonSandbox = sinon.createSandbox();
       disableNative();
diff --git a/test/crypto/gcm.js b/test/crypto/gcm.js
index f564c400..cf4e6600 100644
--- a/test/crypto/gcm.js
+++ b/test/crypto/gcm.js
@@ -77,11 +77,11 @@ export default () => describe('Symmetric AES-GCM (experimental)', function() {
     testAESGCM('12345678901234567890123456789012345678901234567890', true, true);
   });
 
-  describe('Symmetric AES-GCM (asm.js fallback)', function() {
+  describe('Symmetric AES-GCM (non-native)', function() {
     testAESGCM('12345678901234567890123456789012345678901234567890', false, false);
   });
 
-  describe('Symmetric AES-GCM (native encrypt, asm.js decrypt)', function() {
+  describe('Symmetric AES-GCM (native encrypt, non-native decrypt)', function() {
     testAESGCM('12345678901234567890123456789012345678901234567890', true, false);
   });
 });
diff --git a/test/general/openpgp.js b/test/general/openpgp.js
index fe9ae8c2..c141206e 100644
--- a/test/general/openpgp.js
+++ b/test/general/openpgp.js
@@ -2532,7 +2532,7 @@ XfA3pqV4mTzF
       }
     });
 
-    tryTests('CFB mode (asm.js)', tests, {
+    tryTests('CFB mode', tests, {
       if: true,
       beforeEach: function() {
         openpgp.config.aeadProtect = false;
@@ -2582,7 +2582,7 @@ XfA3pqV4mTzF
 
     function tests() {
       describe('encryptSessionKey, decryptSessionKeys', function() {
-        const sk = new Uint8Array([0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01]);
+        const sk = new Uint8Array([0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01,0x01]);
 
         let decryptedPrivateKey; // to avoid decrypting key before each test
         beforeEach(async function() {