diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index c53d15b..09254b2 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -3191,8 +3191,8 @@
     if( status != PSA_SUCCESS )
         return( status );
 
-    if( signature_length < mbedtls_rsa_get_len( rsa ) )
-        return( PSA_ERROR_BUFFER_TOO_SMALL );
+    if( signature_length != mbedtls_rsa_get_len( rsa ) )
+        return( PSA_ERROR_INVALID_SIGNATURE );
 
 #if defined(MBEDTLS_PKCS1_V15)
     if( PSA_ALG_IS_RSA_PKCS1V15_SIGN( alg ) )