diff --git a/cpp/ql/src/semmle/code/cpp/ir/internal/ASTValueNumbering.qll b/cpp/ql/src/semmle/code/cpp/ir/internal/ASTValueNumbering.qll
index 99b70ffaf36..9628fe3fdda 100644
--- a/cpp/ql/src/semmle/code/cpp/ir/internal/ASTValueNumbering.qll
+++ b/cpp/ql/src/semmle/code/cpp/ir/internal/ASTValueNumbering.qll
@@ -61,6 +61,8 @@ class GVN extends TValueNumber {
 
   final string toString() { result = "GVN" }
 
+  final string getDebugString() { result = strictconcat(getAnExpr().toString(), ", ") }
+
   final Location getLocation() {
     result =
       min(Location l |