diff --git a/xmlschemastypes.c b/xmlschemastypes.c
index 1a5454c..834b261 100644
--- a/xmlschemastypes.c
+++ b/xmlschemastypes.c
@@ -3569,8 +3569,8 @@
 
     /* seconds */
     sec = x->value.dur.sec - y->value.dur.sec;
-    carry = (long)sec / SECS_PER_DAY;
-    sec -= (double)(carry * SECS_PER_DAY);
+    carry = (long)(sec / SECS_PER_DAY);
+    sec -= ((double)carry) * SECS_PER_DAY;
 
     /* days */
     day = x->value.dur.day - y->value.dur.day + carry;