diff --git a/src/rpn.rs b/src/rpn.rs
index 0a0dd40..5322ee6 100644
--- a/src/rpn.rs
+++ b/src/rpn.rs
@@ -142,13 +142,10 @@ fn eval(
 				})
 			},
 			_ => {
-				let x = &stack.pop_back().ok_or(EvaluationError {
-					message: "Stack is empty.".to_string(),
-				})?;
-
-				let y = &stack.pop_back().ok_or(EvaluationError {
-					message: "Stack is empty.".to_string(),
-				})?;
+				let (x, y) = (
+					&stack.pop_back().unwrap(),
+					&stack.pop_back().unwrap(),
+				);
 
 				match op {
 					Add => &stack.push_back(y + x),