diff --git a/crypto/cipher-builtin.c b/crypto/cipher-builtin.c
index 37e1a19..39e31a7 100644
--- a/crypto/cipher-builtin.c
+++ b/crypto/cipher-builtin.c
@@ -39,6 +39,7 @@
         QCryptoCipherBuiltinAES aes;
         QCryptoCipherBuiltinDESRFB desrfb;
     } state;
+    size_t blocksize;
     void (*free)(QCryptoCipher *cipher);
     int (*setiv)(QCryptoCipher *cipher,
                  const uint8_t *iv, size_t niv,
@@ -181,6 +182,7 @@
         goto error;
     }
 
+    ctxt->blocksize = AES_BLOCK_SIZE;
     ctxt->free = qcrypto_cipher_free_aes;
     ctxt->setiv = qcrypto_cipher_setiv_aes;
     ctxt->encrypt = qcrypto_cipher_encrypt_aes;
@@ -282,6 +284,7 @@
     memcpy(ctxt->state.desrfb.key, key, nkey);
     ctxt->state.desrfb.nkey = nkey;
 
+    ctxt->blocksize = 8;
     ctxt->free = qcrypto_cipher_free_des_rfb;
     ctxt->setiv = qcrypto_cipher_setiv_des_rfb;
     ctxt->encrypt = qcrypto_cipher_encrypt_des_rfb;
@@ -370,6 +373,12 @@
 {
     QCryptoCipherBuiltin *ctxt = cipher->opaque;
 
+    if (len % ctxt->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctxt->blocksize);
+        return -1;
+    }
+
     return ctxt->encrypt(cipher, in, out, len, errp);
 }
 
@@ -382,6 +391,12 @@
 {
     QCryptoCipherBuiltin *ctxt = cipher->opaque;
 
+    if (len % ctxt->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctxt->blocksize);
+        return -1;
+    }
+
     return ctxt->decrypt(cipher, in, out, len, errp);
 }
 
diff --git a/crypto/cipher-gcrypt.c b/crypto/cipher-gcrypt.c
index 8cfc562..c4f8114 100644
--- a/crypto/cipher-gcrypt.c
+++ b/crypto/cipher-gcrypt.c
@@ -34,6 +34,11 @@
     }
 }
 
+typedef struct QCryptoCipherGcrypt QCryptoCipherGcrypt;
+struct QCryptoCipherGcrypt {
+    gcry_cipher_hd_t handle;
+    size_t blocksize;
+};
 
 QCryptoCipher *qcrypto_cipher_new(QCryptoCipherAlgorithm alg,
                                   QCryptoCipherMode mode,
@@ -41,7 +46,7 @@
                                   Error **errp)
 {
     QCryptoCipher *cipher;
-    gcry_cipher_hd_t handle;
+    QCryptoCipherGcrypt *ctx;
     gcry_error_t err;
     int gcryalg, gcrymode;
 
@@ -87,7 +92,9 @@
     cipher->alg = alg;
     cipher->mode = mode;
 
-    err = gcry_cipher_open(&handle, gcryalg, gcrymode, 0);
+    ctx = g_new0(QCryptoCipherGcrypt, 1);
+
+    err = gcry_cipher_open(&ctx->handle, gcryalg, gcrymode, 0);
     if (err != 0) {
         error_setg(errp, "Cannot initialize cipher: %s",
                    gcry_strerror(err));
@@ -100,10 +107,12 @@
          * bizarre RFB variant of DES :-)
          */
         uint8_t *rfbkey = qcrypto_cipher_munge_des_rfb_key(key, nkey);
-        err = gcry_cipher_setkey(handle, rfbkey, nkey);
+        err = gcry_cipher_setkey(ctx->handle, rfbkey, nkey);
         g_free(rfbkey);
+        ctx->blocksize = 8;
     } else {
-        err = gcry_cipher_setkey(handle, key, nkey);
+        err = gcry_cipher_setkey(ctx->handle, key, nkey);
+        ctx->blocksize = 16;
     }
     if (err != 0) {
         error_setg(errp, "Cannot set key: %s",
@@ -111,11 +120,12 @@
         goto error;
     }
 
-    cipher->opaque = handle;
+    cipher->opaque = ctx;
     return cipher;
 
  error:
-    gcry_cipher_close(handle);
+    gcry_cipher_close(ctx->handle);
+    g_free(ctx);
     g_free(cipher);
     return NULL;
 }
@@ -123,12 +133,13 @@
 
 void qcrypto_cipher_free(QCryptoCipher *cipher)
 {
-    gcry_cipher_hd_t handle;
+    QCryptoCipherGcrypt *ctx;
     if (!cipher) {
         return;
     }
-    handle = cipher->opaque;
-    gcry_cipher_close(handle);
+    ctx = cipher->opaque;
+    gcry_cipher_close(ctx->handle);
+    g_free(ctx);
     g_free(cipher);
 }
 
@@ -139,10 +150,16 @@
                            size_t len,
                            Error **errp)
 {
-    gcry_cipher_hd_t handle = cipher->opaque;
+    QCryptoCipherGcrypt *ctx = cipher->opaque;
     gcry_error_t err;
 
-    err = gcry_cipher_encrypt(handle,
+    if (len % ctx->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctx->blocksize);
+        return -1;
+    }
+
+    err = gcry_cipher_encrypt(ctx->handle,
                               out, len,
                               in, len);
     if (err != 0) {
@@ -161,10 +178,16 @@
                            size_t len,
                            Error **errp)
 {
-    gcry_cipher_hd_t handle = cipher->opaque;
+    QCryptoCipherGcrypt *ctx = cipher->opaque;
     gcry_error_t err;
 
-    err = gcry_cipher_decrypt(handle,
+    if (len % ctx->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctx->blocksize);
+        return -1;
+    }
+
+    err = gcry_cipher_decrypt(ctx->handle,
                               out, len,
                               in, len);
     if (err != 0) {
@@ -180,11 +203,17 @@
                          const uint8_t *iv, size_t niv,
                          Error **errp)
 {
-    gcry_cipher_hd_t handle = cipher->opaque;
+    QCryptoCipherGcrypt *ctx = cipher->opaque;
     gcry_error_t err;
 
-    gcry_cipher_reset(handle);
-    err = gcry_cipher_setiv(handle, iv, niv);
+    if (niv != ctx->blocksize) {
+        error_setg(errp, "Expected IV size %zu not %zu",
+                   ctx->blocksize, niv);
+        return -1;
+    }
+
+    gcry_cipher_reset(ctx->handle);
+    err = gcry_cipher_setiv(ctx->handle, iv, niv);
     if (err != 0) {
         error_setg(errp, "Cannot set IV: %s",
                    gcry_strerror(err));
diff --git a/crypto/cipher-nettle.c b/crypto/cipher-nettle.c
index b01cb1c..7449338 100644
--- a/crypto/cipher-nettle.c
+++ b/crypto/cipher-nettle.c
@@ -69,7 +69,7 @@
     nettle_cipher_func *alg_encrypt;
     nettle_cipher_func *alg_decrypt;
     uint8_t *iv;
-    size_t niv;
+    size_t blocksize;
 };
 
 bool qcrypto_cipher_supports(QCryptoCipherAlgorithm alg)
@@ -125,7 +125,7 @@
         ctx->alg_encrypt = des_encrypt_wrapper;
         ctx->alg_decrypt = des_decrypt_wrapper;
 
-        ctx->niv = DES_BLOCK_SIZE;
+        ctx->blocksize = DES_BLOCK_SIZE;
         break;
 
     case QCRYPTO_CIPHER_ALG_AES_128:
@@ -140,14 +140,14 @@
         ctx->alg_encrypt = aes_encrypt_wrapper;
         ctx->alg_decrypt = aes_decrypt_wrapper;
 
-        ctx->niv = AES_BLOCK_SIZE;
+        ctx->blocksize = AES_BLOCK_SIZE;
         break;
     default:
         error_setg(errp, "Unsupported cipher algorithm %d", alg);
         goto error;
     }
 
-    ctx->iv = g_new0(uint8_t, ctx->niv);
+    ctx->iv = g_new0(uint8_t, ctx->blocksize);
     cipher->opaque = ctx;
 
     return cipher;
@@ -184,6 +184,12 @@
 {
     QCryptoCipherNettle *ctx = cipher->opaque;
 
+    if (len % ctx->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctx->blocksize);
+        return -1;
+    }
+
     switch (cipher->mode) {
     case QCRYPTO_CIPHER_MODE_ECB:
         ctx->alg_encrypt(ctx->ctx_encrypt, len, out, in);
@@ -191,7 +197,7 @@
 
     case QCRYPTO_CIPHER_MODE_CBC:
         cbc_encrypt(ctx->ctx_encrypt, ctx->alg_encrypt,
-                    ctx->niv, ctx->iv,
+                    ctx->blocksize, ctx->iv,
                     len, out, in);
         break;
     default:
@@ -211,6 +217,12 @@
 {
     QCryptoCipherNettle *ctx = cipher->opaque;
 
+    if (len % ctx->blocksize) {
+        error_setg(errp, "Length %zu must be a multiple of block size %zu",
+                   len, ctx->blocksize);
+        return -1;
+    }
+
     switch (cipher->mode) {
     case QCRYPTO_CIPHER_MODE_ECB:
         ctx->alg_decrypt(ctx->ctx_decrypt ? ctx->ctx_decrypt : ctx->ctx_encrypt,
@@ -219,7 +231,7 @@
 
     case QCRYPTO_CIPHER_MODE_CBC:
         cbc_decrypt(ctx->ctx_decrypt ? ctx->ctx_decrypt : ctx->ctx_encrypt,
-                    ctx->alg_decrypt, ctx->niv, ctx->iv,
+                    ctx->alg_decrypt, ctx->blocksize, ctx->iv,
                     len, out, in);
         break;
     default:
@@ -235,9 +247,9 @@
                          Error **errp)
 {
     QCryptoCipherNettle *ctx = cipher->opaque;
-    if (niv != ctx->niv) {
+    if (niv != ctx->blocksize) {
         error_setg(errp, "Expected IV size %zu not %zu",
-                   ctx->niv, niv);
+                   ctx->blocksize, niv);
         return -1;
     }
     memcpy(ctx->iv, iv, niv);
diff --git a/tests/test-crypto-cipher.c b/tests/test-crypto-cipher.c
index 1b60c34..f4946a0 100644
--- a/tests/test-crypto-cipher.c
+++ b/tests/test-crypto-cipher.c
@@ -313,6 +313,53 @@
     qcrypto_cipher_free(cipher);
 }
 
+static void test_cipher_short_plaintext(void)
+{
+    Error *err = NULL;
+    QCryptoCipher *cipher;
+    uint8_t key[32] = { 0 };
+    uint8_t plaintext1[20] = { 0 };
+    uint8_t ciphertext1[20] = { 0 };
+    uint8_t plaintext2[40] = { 0 };
+    uint8_t ciphertext2[40] = { 0 };
+    int ret;
+
+    cipher = qcrypto_cipher_new(
+        QCRYPTO_CIPHER_ALG_AES_256,
+        QCRYPTO_CIPHER_MODE_CBC,
+        key, sizeof(key),
+        &error_abort);
+    g_assert(cipher != NULL);
+
+    /* Should report an error as plaintext is shorter
+     * than block size
+     */
+    ret = qcrypto_cipher_encrypt(cipher,
+                                 plaintext1,
+                                 ciphertext1,
+                                 sizeof(plaintext1),
+                                 &err);
+    g_assert(ret == -1);
+    g_assert(err != NULL);
+
+    error_free(err);
+    err = NULL;
+
+    /* Should report an error as plaintext is larger than
+     * block size, but not a multiple of block size
+     */
+    ret = qcrypto_cipher_encrypt(cipher,
+                                 plaintext2,
+                                 ciphertext2,
+                                 sizeof(plaintext2),
+                                 &err);
+    g_assert(ret == -1);
+    g_assert(err != NULL);
+
+    error_free(err);
+    qcrypto_cipher_free(cipher);
+}
+
 int main(int argc, char **argv)
 {
     size_t i;
@@ -328,5 +375,8 @@
     g_test_add_func("/crypto/cipher/null-iv",
                     test_cipher_null_iv);
 
+    g_test_add_func("/crypto/cipher/short-plaintext",
+                    test_cipher_short_plaintext);
+
     return g_test_run();
 }