diff --git a/nssa/program_methods/guest/src/bin/privacy_preserving_circuit.rs b/nssa/program_methods/guest/src/bin/privacy_preserving_circuit.rs
index 97a49a0..7bca005 100644
--- a/nssa/program_methods/guest/src/bin/privacy_preserving_circuit.rs
+++ b/nssa/program_methods/guest/src/bin/privacy_preserving_circuit.rs
@@ -29,7 +29,7 @@ fn main() {
         panic!("Max depth is exceeded");
     }
 
-    if program_outputs[num_calls - 1].chained_call.is_some() {
+    if program_outputs.last().and_then(|last| last.chained_call.as_ref()).is_some() {
         panic!("Call stack is incomplete");
     }