diff --git a/src/libexpr/value.hh b/src/libexpr/value.hh
index 227f5e173..408b5e087 100644
--- a/src/libexpr/value.hh
+++ b/src/libexpr/value.hh
@@ -119,7 +119,7 @@ static inline void mkBool(Value & v, bool b)
 static inline void mkNull(Value & v)
 {
     v.type = tNull;
-    v.app.left = v.app.right = 00; // scrub
+    v.app.left = v.app.right = 0; // scrub
 }