diff --git a/src/rpn.rs b/src/rpn.rs
index 7cba297..e369c23 100644
--- a/src/rpn.rs
+++ b/src/rpn.rs
@@ -138,6 +138,7 @@ fn eval(
 	// Split the input into tokens.
 	let mut toks: VecDeque<CalcType> = input
 		.split(' ')
+		.rev()
 		.map(|t| CalcType::from(t))
 		.collect();
 	let mut ops: VecDeque<CalcType> = VecDeque::new();