diff --git a/gcc/tree-vect-generic.cc b/gcc/tree-vect-generic.cc
index df04a0db68da3222f43dd938f8e7adb186cd93c9..da1fd2f40d82a9fa301e6ed0b2f4c3c222d58a8d 100644
--- a/gcc/tree-vect-generic.cc
+++ b/gcc/tree-vect-generic.cc
@@ -481,7 +481,7 @@ expand_vector_comparison (gimple_stmt_iterator *gsi, tree type, tree op0,
 	    }
 	  t = gimplify_build1 (gsi, VIEW_CONVERT_EXPR, type, t);
 	}
-      else
+      else if (TYPE_VECTOR_SUBPARTS (type).is_constant ())
 	t = expand_vector_piecewise (gsi, do_compare, type,
 				     TREE_TYPE (TREE_TYPE (op0)), op0, op1,
 				     code, false);