diff --git a/repo2docker/__main__.py b/repo2docker/__main__.py
index 1cb4862d..5911c81a 100644
--- a/repo2docker/__main__.py
+++ b/repo2docker/__main__.py
@@ -300,7 +300,7 @@ def make_r2d(argv=None):
 
     if args.build_memory_limit:
         # if the string only contains numerals we assume it should be an int
-        # and specifies a size inn bytes
+        # and specifies a size in bytes
         if args.build_memory_limit.isnumeric():
             r2d.build_memory_limit = int(args.build_memory_limit)
         else: