diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 5b92f49..ef34f85 100755
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -1516,7 +1516,7 @@
         mbedtls_rsa_context *rsa = slot->data.rsa;
         int ret;
 
-        if( output_size < rsa->len )
+        if( input_length != rsa->len )
             return( PSA_ERROR_INVALID_ARGUMENT );
 
 #if defined(MBEDTLS_PKCS1_V15)