diff --git a/pigz.c b/pigz.c
index a9b0f2f..c82c1eb 100644
--- a/pigz.c
+++ b/pigz.c
@@ -1333,7 +1333,7 @@
         }
         ver++;
     } while (left);
-    return left < 2 ? num << (left << 2) : -1;
+    return left < 3 ? num << (left << 2) : -1;
 }
 
 // -- check value combination routines for parallel calculation --