diff --git a/gcc/tree-ssa-alias.cc b/gcc/tree-ssa-alias.cc
index b5476e8b41e..e1bc04b82ba 100644
--- a/gcc/tree-ssa-alias.cc
+++ b/gcc/tree-ssa-alias.cc
@@ -2829,6 +2829,9 @@ ref_maybe_used_by_call_p_1 (gcall *call, ao_ref *ref, bool tbaa_p)
 	      ao_ref_init_from_ptr_and_size (&rhs_ref,
 					     gimple_call_arg (call, 0),
 					     TYPE_SIZE_UNIT (TREE_TYPE (lhs)));
+	      /* We cannot make this a known-size access since otherwise
+		 we disambiguate against refs to decls that are smaller.  */
+	      rhs_ref.size = -1;
 	      rhs_ref.ref_alias_set = rhs_ref.base_alias_set
 		= tbaa_p ? get_deref_alias_set (TREE_TYPE
 					(gimple_call_arg (call, 1))) : 0;
@@ -3073,7 +3076,7 @@ call_may_clobber_ref_p_1 (gcall *call, ao_ref *ref, bool tbaa_p)
 	  ao_ref_init_from_ptr_and_size (&lhs_ref, gimple_call_arg (call, 0),
 					 TYPE_SIZE_UNIT (TREE_TYPE (rhs)));
 	  /* We cannot make this a known-size access since otherwise
-	     we disambiguate against stores to decls that are smaller.  */
+	     we disambiguate against refs to decls that are smaller.  */
 	  lhs_ref.size = -1;
 	  lhs_ref.ref_alias_set = lhs_ref.base_alias_set
 	    = tbaa_p ? get_deref_alias_set