diff --git a/src/terminator/mod.rs b/src/terminator/mod.rs
index 4aae47ba96c..188104ef9eb 100644
--- a/src/terminator/mod.rs
+++ b/src/terminator/mod.rs
@@ -572,7 +572,7 @@ impl<'a, 'tcx> EvalContext<'a, 'tcx> {
 
             "free" => {
                 let ptr = args[0].read_ptr(&self.memory)?;
-                if !ptr.is_null() {
+                if !ptr.is_null()? {
                     self.memory.deallocate(ptr.to_ptr()?)?;
                 }
             }