diff --git a/libgit2-sys/lib.rs b/libgit2-sys/lib.rs
index 383db6c37e..2cc53bf92d 100644
--- a/libgit2-sys/lib.rs
+++ b/libgit2-sys/lib.rs
@@ -742,7 +742,7 @@ git_enum! {
 }
 
 pub type git_treewalk_cb =
-    Option<extern "C" fn(*const c_char, *const git_tree_entry, *mut c_void) -> c_int>;
+    extern "C" fn(*const c_char, *const git_tree_entry, *mut c_void) -> c_int;
 pub type git_treebuilder_filter_cb =
     Option<extern "C" fn(*const git_tree_entry, *mut c_void) -> c_int>;
 
diff --git a/src/tree.rs b/src/tree.rs
index ae8fe3b4c5..e683257436 100644
--- a/src/tree.rs
+++ b/src/tree.rs
@@ -36,6 +36,7 @@ pub struct TreeIter<'tree> {
 
 /// A binary indicator of whether a tree walk should be performed in pre-order
 /// or post-order.
+#[derive(Clone, Copy)]
 pub enum TreeWalkMode {
     /// Runs the traversal in pre-order.
     PreOrder = 0,
@@ -126,12 +127,12 @@ impl<'repo> Tree<'repo> {
             let mut data = TreeWalkCbData {
                 callback: &mut callback,
             };
-            raw::git_tree_walk(
+            try_call!(raw::git_tree_walk(
                 self.raw(),
-                mode.into(),
-                Some(treewalk_cb::<T>),
-                &mut data as *mut _ as *mut c_void,
-            );
+                mode as raw::git_treewalk_mode,
+                treewalk_cb::<T>,
+                &mut data as *mut _ as *mut c_void
+            ));
             Ok(())
         }
     }
@@ -599,4 +600,18 @@ mod tests {
         .unwrap();
         assert_eq!(ct, 8);
     }
+
+    #[test]
+    fn tree_walk_error() {
+        let (td, repo) = crate::test::repo_init();
+
+        setup_repo(&td, &repo);
+
+        let head = repo.head().unwrap();
+        let target = head.target().unwrap();
+        let commit = repo.find_commit(target).unwrap();
+        let tree = repo.find_tree(commit.tree_id()).unwrap();
+        let e = tree.walk(TreeWalkMode::PreOrder, |_, _| -1).unwrap_err();
+        assert_eq!(e.class(), crate::ErrorClass::Callback);
+    }
 }