diff --git a/src/marble_engine.rs b/src/marble_engine.rs
index 9a4ce86..3e439a7 100644
--- a/src/marble_engine.rs
+++ b/src/marble_engine.rs
@@ -63,6 +63,7 @@ impl Machine {
 	}
 
 	pub fn set_input(&mut self, bytes: Vec<u8>) {
+		self.input_index = self.input_index.min(bytes.len());
 		self.input = bytes;
 	}