diff --git a/dlls/bcrypt/bcrypt_main.c b/dlls/bcrypt/bcrypt_main.c
index 1aeafd0dd82..69d5129a7d4 100644
--- a/dlls/bcrypt/bcrypt_main.c
+++ b/dlls/bcrypt/bcrypt_main.c
@@ -1003,11 +1003,21 @@ static gnutls_cipher_algorithm_t get_gnutls_cipher( const struct key *key )
         WARN( "handle block size\n" );
         switch (key->mode)
         {
-            case MODE_ID_GCM: return GNUTLS_CIPHER_AES_128_GCM;
+            case MODE_ID_GCM:
+                if (key->secret_len == 16) return GNUTLS_CIPHER_AES_128_GCM;
+                if (key->secret_len == 32) return GNUTLS_CIPHER_AES_256_GCM;
+                break;
             case MODE_ID_ECB: /* can be emulated with CBC + empty IV */
             case MODE_ID_CBC:
-            default:          return GNUTLS_CIPHER_AES_128_CBC;
+                if (key->secret_len == 16) return GNUTLS_CIPHER_AES_128_CBC;
+                if (key->secret_len == 24) return GNUTLS_CIPHER_AES_192_CBC;
+                if (key->secret_len == 32) return GNUTLS_CIPHER_AES_256_CBC;
+                break;
+            default:
+                break;
         }
+        FIXME( "aes mode %u with key length %u not supported\n", key->mode, key->secret_len );
+        return GNUTLS_CIPHER_UNKNOWN;
     default:
         FIXME( "algorithm %u not supported\n", key->alg_id );
         return GNUTLS_CIPHER_UNKNOWN;
diff --git a/dlls/bcrypt/tests/bcrypt.c b/dlls/bcrypt/tests/bcrypt.c
index 3abbd759e90..971dee5b1d3 100644
--- a/dlls/bcrypt/tests/bcrypt.c
+++ b/dlls/bcrypt/tests/bcrypt.c
@@ -622,6 +622,9 @@ static void test_BCryptEncrypt(void)
         {0x60,0x50,0x40,0x30,0x20,0x10,0x60,0x50,0x40,0x30,0x20,0x10};
     static UCHAR secret[] =
         {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f};
+    static UCHAR secret256[] =
+        {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f,
+         0x0f,0x0e,0x0d,0x0c,0x0b,0x0a,0x09,0x08,0x07,0x06,0x05,0x04,0x03,0x02,0x01,0x00};
     static UCHAR iv[] =
         {0x00,0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b,0x0c,0x0d,0x0e,0x0f};
     static UCHAR data[] =
@@ -654,6 +657,10 @@ static void test_BCryptEncrypt(void)
         {0xb5,0x8a,0x10,0x64,0xd8,0xac,0xa9,0x9b,0xd9,0xb0,0x40,0x5b,0x85,0x45,0xf5,0xbb};
     static UCHAR expected9[] =
         {0x0a,0x94,0x0b,0xb5,0x41,0x6e,0xf0,0x45,0xf1,0xc3,0x94,0x58,0xc6,0x53,0xea,0x5a};
+    static UCHAR expected10[] =
+        {0x66,0xb8,0xbd,0xe5,0x90,0x6c,0xec,0xdf,0xfa,0x8a,0xb2,0xfd,0x92,0x84,0xeb,0xf0,
+         0x95,0xc4,0xdf,0xa7,0x7a,0x62,0xe4,0xab,0xd4,0x0e,0x94,0x4e,0xd7,0x6e,0xa1,0x47,
+         0x29,0x4b,0x37,0xfe,0x28,0x6d,0x5f,0x69,0x46,0x30,0x73,0xc0,0xaa,0x42,0xe4,0x46};
     static UCHAR expected_tag[] =
         {0x89,0xb3,0x92,0x00,0x39,0x20,0x09,0xb4,0x6a,0xd6,0xaf,0xca,0x4b,0x5b,0xfd,0xd0};
     static UCHAR expected_tag2[] =
@@ -785,6 +792,31 @@ static void test_BCryptEncrypt(void)
     ok(ret == STATUS_SUCCESS, "got %08x\n", ret);
     HeapFree(GetProcessHeap(), 0, buf);
 
+    /* 256 bit key */
+    buf = HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, len);
+    ret = pBCryptGenerateSymmetricKey(aes, &key, buf, len, secret256, sizeof(secret256), 0);
+    ok(ret == STATUS_SUCCESS, "got %08x\n", ret);
+
+    size = 0;
+    memcpy(ivbuf, iv, sizeof(iv));
+    ret = pBCryptEncrypt(key, data2, 32, NULL, ivbuf, 16, NULL, 0, &size, BCRYPT_BLOCK_PADDING);
+    ok(ret == STATUS_SUCCESS, "got %08x\n", ret);
+    ok(size == 48, "got %u\n", size);
+
+    size = 0;
+    memcpy(ivbuf, iv, sizeof(iv));
+    memset(ciphertext, 0, sizeof(ciphertext));
+    ret = pBCryptEncrypt(key, data2, 32, NULL, ivbuf, 16, ciphertext, 48, &size, BCRYPT_BLOCK_PADDING);
+    ok(ret == STATUS_SUCCESS, "got %08x\n", ret);
+    ok(size == 48, "got %u\n", size);
+    ok(!memcmp(ciphertext, expected10, sizeof(expected10)), "wrong data\n");
+    for (i = 0; i < 48; i++)
+        ok(ciphertext[i] == expected10[i], "%u: %02x != %02x\n", i, ciphertext[i], expected10[i]);
+
+    ret = pBCryptDestroyKey(key);
+    ok(ret == STATUS_SUCCESS, "got %08x\n", ret);
+    HeapFree(GetProcessHeap(), 0, buf);
+
     /******************
      * AES - GCM mode *
      ******************/