diff --git a/src/goto-programs/graphml_witness.cpp b/src/goto-programs/graphml_witness.cpp
index ccae6ad7e55..2c382d76f98 100644
--- a/src/goto-programs/graphml_witness.cpp
+++ b/src/goto-programs/graphml_witness.cpp
@@ -278,24 +278,17 @@ void graphml_witnesst::operator()(const goto_tracet &goto_trace)
         }
 
         if(it->type==goto_trace_stept::typet::ASSIGNMENT &&
-           it->lhs_object_value.is_not_nil() &&
+           it->full_lhs_value.is_not_nil() &&
            it->full_lhs.is_not_nil())
         {
-          if(!it->lhs_object_value.is_constant() ||
-             !it->lhs_object_value.has_operands() ||
-             !has_prefix(id2string(it->lhs_object_value.op0().get(ID_value)),
-                         "INVALID-"))
-          {
-            xmlt &val=edge.new_element("data");
-            val.set_attribute("key", "assumption");
-            code_assignt assign(it->lhs_object, it->lhs_object_value);
-            irep_idt identifier=it->lhs_object.get_identifier();
-            val.data=convert_assign_rec(identifier, assign);
-
-            xmlt &val_s=edge.new_element("data");
-            val_s.set_attribute("key", "assumption.scope");
-            val_s.data=id2string(it->pc->source_location.get_function());
-          }
+          xmlt &val=edge.new_element("data");
+          val.set_attribute("key", "assumption");
+          val.data=from_expr(ns, it->pc->function, it->full_lhs)+" = "+
+                   from_expr(ns, it->pc->function, it->full_lhs_value)+";";
+
+          xmlt &val_s=edge.new_element("data");
+          val_s.set_attribute("key", "assumption.scope");
+          val_s.data=id2string(it->pc->source_location.get_function());
         }
         else if(it->type==goto_trace_stept::typet::GOTO &&
                 it->pc->is_goto())