diff --git a/ethermess.c b/ethermess.c
index 0dfaf3c..0656e89 100644
--- a/ethermess.c
+++ b/ethermess.c
@@ -193,7 +193,7 @@ intmax_t saturating_sub(intmax_t a, intmax_t b) {
 		intmax_t c = saturating_sub(b, -INTMAX_MAX);
 		return saturating_sub(saturating_add(a, c - b), c);
 	} else {
-		return saturating_sub(a, -b);
+		return saturating_add(a, -b);
 	}
 }