diff --git a/gcc/tree-vect-generic.cc b/gcc/tree-vect-generic.cc
index 173ebd9a7ba..80c2d31776b 100644
--- a/gcc/tree-vect-generic.cc
+++ b/gcc/tree-vect-generic.cc
@@ -1759,6 +1759,7 @@ expand_vector_conversion (gimple_stmt_iterator *gsi)
 					      converts))
     {
       new_rhs = arg;
+      gcc_assert (!converts.is_empty ());
       for (unsigned int i = 0; i < converts.length () - 1; i++)
 	{
 	  new_lhs = make_ssa_name (converts[i].first);