diff --git a/library/rsa.c b/library/rsa.c
index c1fe6b8ff..26d69c522 100644
--- a/library/rsa.c
+++ b/library/rsa.c
@@ -525,7 +525,8 @@ int rsa_rsaes_oaep_encrypt( rsa_context *ctx,
     olen = ctx->len;
     hlen = md_get_size( md_info );
 
-    if( olen < ilen + 2 * hlen + 2 )
+    // first comparison checks for overflow
+    if( ilen + 2 * hlen + 2 < ilen || olen < ilen + 2 * hlen + 2 )
         return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
 
     memset( output, 0, olen );
@@ -592,7 +593,8 @@ int rsa_rsaes_pkcs1_v15_encrypt( rsa_context *ctx,
 
     olen = ctx->len;
 
-    if( olen < ilen + 11 )
+    // first comparison checks for overflow
+    if( ilen + 11 < ilen || olen < ilen + 11 )
         return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
 
     nb_pad = olen - 3 - ilen;