diff --git a/js/src/jstracer.cpp b/js/src/jstracer.cpp
index f7396541cd4..f4dcd760795 100644
--- a/js/src/jstracer.cpp
+++ b/js/src/jstracer.cpp
@@ -11383,6 +11383,7 @@ TraceRecorder::callNative(uintN argc, JSOp mode)
             }
         }
     }
+    set(&vp[1], this_ins);
     box_value_into(vp[1], this_ins, invokevp_ins, 1 * sizeof(Value), ACC_OTHER);
 
     // Populate argv.