diff --git a/library/bignum.c b/library/bignum.c
index 993eb2aed9..3f81d5de3b 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -2253,7 +2253,7 @@ cleanup:
     for( i = w_table_used_size/2; i < w_table_used_size; i++ )
         mbedtls_mpi_free( &W[i] );
 
-    mbedtls_mpi_free( &W[0] );
+    mbedtls_mpi_free( &W[x_index] );
     mbedtls_mpi_free( &W[1] );
     mbedtls_mpi_free( &T );
     mbedtls_mpi_free( &Apos );