diff --git a/library/cipher.c b/library/cipher.c
index 7164741b1..e0fd39dc9 100644
--- a/library/cipher.c
+++ b/library/cipher.c
@@ -186,6 +186,7 @@ int mbedtls_cipher_setup( mbedtls_cipher_context_t *ctx, const mbedtls_cipher_in
         return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
 
     mbedtls_platform_memset( ctx, 0, sizeof( mbedtls_cipher_context_t ) );
+    ctx->operation = MBEDTLS_OPERATION_NONE;
 
     if( NULL == ( ctx->cipher_ctx = cipher_info->base->ctx_alloc_func() ) )
         return( MBEDTLS_ERR_CIPHER_ALLOC_FAILED );