diff --git a/src/io/argf.cr b/src/io/argf.cr
index a0af097ed594..afa92c2a545b 100644
--- a/src/io/argf.cr
+++ b/src/io/argf.cr
@@ -25,7 +25,7 @@ class IO::ARGF < IO
       read_count = 0
     end
 
-    read_count
+    read_count.to_i32
   end
 
   # :nodoc: