diff --git a/com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/control/ReplacementDispatchNode.java b/com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/control/ReplacementDispatchNode.java
index 656bb60251dcb3dce02e777cbf5a03097e58f4ad..144d1200fdcce2011999435a3a09005abb38332c 100644
--- a/com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/control/ReplacementDispatchNode.java
+++ b/com.oracle.truffle.r.nodes/src/com/oracle/truffle/r/nodes/control/ReplacementDispatchNode.java
@@ -84,7 +84,7 @@ public final class ReplacementDispatchNode extends OperatorNode {
 
     public RNode create(boolean isVoid) {
         RNode replacement;
-        if (lhs instanceof RSyntaxCall) {
+        if (lhs.asRSyntaxNode() instanceof RSyntaxCall) {
             replacement = createReplacementNode(isVoid);
         } else {
             replacement = new WriteVariableSyntaxNode(getLazySourceSection(), operator, lhs.asRSyntaxNode(), rhs, isSuper);