diff --git a/library/rsa.c b/library/rsa.c
index 9150e87..2baf532 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -856,6 +856,9 @@
         bad |= *p++; /* Must be zero */
     }
 
+    if( pad_count < 8 )
+        return( MBEDTLS_ERR_RSA_BAD_INPUT_DATA );
+
     if( bad )
         return( MBEDTLS_ERR_RSA_INVALID_PADDING );