diff --git a/com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java b/com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java
index 218c85fb302cb5341c0f4bf8f7a07b4fc223ea7d..c91b540d984603509828bab1babf4d7ee0d53cef 100644
--- a/com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java
+++ b/com.oracle.truffle.r.engine/src/com/oracle/truffle/r/engine/REngine.java
@@ -368,7 +368,7 @@ final class REngine implements RContext.Engine {
     }
 
     private static class PromiseStatement extends RNode implements RSyntaxNode {
-        private final RNode promise;
+        @Child private RNode promise;
 
         PromiseStatement(RNode promise) {
             this.promise = promise;