diff --git a/src/image.rs b/src/image.rs
index e385daa..f84aa7d 100644
--- a/src/image.rs
+++ b/src/image.rs
@@ -50,7 +50,7 @@ impl Image {
         self.data.as_mut_slice()
     }
 
-    pub fn data(&mut self) -> &[u8] {
+    pub fn data(&self) -> &[u8] {
         self.data.as_slice()
     }