diff --git a/doc/Changelog b/doc/Changelog
index 2236e5550..3fa86ac3b 100644
--- a/doc/Changelog
+++ b/doc/Changelog
@@ -1,5 +1,6 @@
 3 March 2022: Wouter
 	- Fix #637: Integer Overflow in sldns_str2period function.
+	- Fix for #637: fix integer overflow checks in sldns_str2period.
 
 2 March 2022: George
 	- Merge PR #632 from scottrw93: Match cnames in ipset.
diff --git a/sldns/parseutil.c b/sldns/parseutil.c
index e69c568db..dd1f33484 100644
--- a/sldns/parseutil.c
+++ b/sldns/parseutil.c
@@ -291,7 +291,7 @@ sldns_str2period(const char *nptr, const char **endptr, int* overflow)
 			case '7':
 			case '8':
 			case '9':
-				if(i > maxint/10 || i > maxint - (**endptr - '0')) {
+				if(i > maxint/10 || i*10 > maxint - (**endptr - '0')) {
 					*overflow = 1;
 					return 0;
 				}