diff --git a/src/solvers/flattening/bv_pointers.cpp b/src/solvers/flattening/bv_pointers.cpp
index 4567c89d7a4..78332162fdf 100644
--- a/src/solvers/flattening/bv_pointers.cpp
+++ b/src/solvers/flattening/bv_pointers.cpp
@@ -37,7 +37,7 @@ literalt bv_pointerst::convert_rest(const exprt &expr)
 
   const exprt::operandst &operands=expr.operands();
 
-  if(expr.id()=="invalid-pointer")
+  if(expr.id()==ID_invalid_pointer)
   {
     if(operands.size()==1 &&
        is_ptr(operands[0].type()))
diff --git a/src/solvers/smt1/smt1_conv.cpp b/src/solvers/smt1/smt1_conv.cpp
index a2e817ce724..6d8f3336f9f 100644
--- a/src/solvers/smt1/smt1_conv.cpp
+++ b/src/solvers/smt1/smt1_conv.cpp
@@ -1084,7 +1084,7 @@ void smt1_convt::convert_expr(const exprt &expr, bool bool_as_bv)
   {
     convert_is_dynamic_object(expr, bool_as_bv);
   }
-  else if(expr.id()=="invalid-pointer")
+  else if(expr.id()==ID_invalid_pointer)
   {
     const typet &type=expr.type();
 
diff --git a/src/solvers/smt2/smt2_conv.cpp b/src/solvers/smt2/smt2_conv.cpp
index e0dff532113..41c0e933d67 100644
--- a/src/solvers/smt2/smt2_conv.cpp
+++ b/src/solvers/smt2/smt2_conv.cpp
@@ -1573,7 +1573,7 @@ void smt2_convt::convert_expr(const exprt &expr)
   {
     convert_is_dynamic_object(expr);
   }
-  else if(expr.id()=="invalid-pointer")
+  else if(expr.id()==ID_invalid_pointer)
   {
     assert(expr.operands().size()==1);