diff --git a/include/pt-sgi.h b/include/pt-sgi.h
index 36b1a67fb..15f355b84 100644
--- a/include/pt-sgi.h
+++ b/include/pt-sgi.h
@@ -100,7 +100,7 @@ static inline uint32_t sgi_pt_checksum(struct sgi_disklabel *label)
 	i = sizeof(*label) / sizeof(*ptr);
 
 	while (i--)
-		sum += be32_to_cpu(ptr[i]);
+		sum -= be32_to_cpu(ptr[i]);
 
 	return sum;
 }