diff --git a/library/aes.c b/library/aes.c
index 1c743f9..0543cd7 100644
--- a/library/aes.c
+++ b/library/aes.c
@@ -1298,7 +1298,7 @@
 
     n = *iv_off;
 
-    if( n > 16 )
+    if( n > 15 )
         return( MBEDTLS_ERR_AES_BAD_INPUT_DATA );
 
     if( mode == MBEDTLS_AES_DECRYPT )
@@ -1394,7 +1394,7 @@
 
     n = *iv_off;
 
-    if( n > 16 )
+    if( n > 15 )
         return( MBEDTLS_ERR_AES_BAD_INPUT_DATA );
 
     while( length-- )
diff --git a/tests/suites/test_suite_aes.function b/tests/suites/test_suite_aes.function
index 3762ba4..f74183d 100644
--- a/tests/suites/test_suite_aes.function
+++ b/tests/suites/test_suite_aes.function
@@ -569,6 +569,7 @@
 #endif
     const unsigned char in[16] = { 0 };
     unsigned char out[16];
+    size_t size;
 
     /* These calls accept NULL */
     TEST_VALID_PARAM( mbedtls_aes_free( NULL ) );
@@ -597,6 +598,19 @@
                                         in, in, out )
                  == MBEDTLS_ERR_AES_INVALID_INPUT_LENGTH );
 #endif
+
+#if defined(MBEDTLS_CIPHER_MODE_CFB)
+    size = 16;
+    TEST_ASSERT( mbedtls_aes_crypt_cfb128( &aes_ctx, MBEDTLS_AES_ENCRYPT, 16,
+                                           &size, out, in, out )
+                 == MBEDTLS_ERR_AES_BAD_INPUT_DATA );
+#endif
+
+#if defined(MBEDTLS_CIPHER_MODE_OFB)
+    size = 16;
+    TEST_ASSERT( mbedtls_aes_crypt_ofb( &aes_ctx, 16, &size, out, in, out )
+                 == MBEDTLS_ERR_AES_BAD_INPUT_DATA );
+#endif
 }
 /* END_CASE */