diff --git a/pygit2/repository.py b/pygit2/repository.py
index c7330e187..a9ca2b7bd 100644
--- a/pygit2/repository.py
+++ b/pygit2/repository.py
@@ -381,14 +381,12 @@ def whatever_to_tree_or_blob(obj):
             try:
                 obj = obj.peel(Blob)
             except Exception:
-                pass
-
-            # And if that failed, try to get a tree, raising a type
-            # error if that still doesn't work
-            try:
-                obj = obj.peel(Tree)
-            except Exception:
-                raise TypeError('unexpected "%s"' % type(obj))
+              # And if that failed, try to get a tree, raising a type
+              # error if that still doesn't work
+              try:
+                  obj = obj.peel(Tree)
+              except Exception:
+                  raise TypeError('unexpected "%s"' % type(obj))
 
             return obj
 
@@ -415,7 +413,7 @@ def whatever_to_tree_or_blob(obj):
 
         # Case 4: Diff blob to blob
         if isinstance(a, Blob) and isinstance(b, Blob):
-            raise NotImplementedError('git_diff_blob_to_blob()')
+            return a.diff(b)
 
         raise ValueError("Only blobs and treeish can be diffed")