diff --git a/src/backend/utils/adt/xid.c b/src/backend/utils/adt/xid.c
index 6b617653b7..3a7d8bca5b 100644
--- a/src/backend/utils/adt/xid.c
+++ b/src/backend/utils/adt/xid.c
@@ -41,13 +41,10 @@ Datum
 xidout(PG_FUNCTION_ARGS)
 {
 	TransactionId transactionId = PG_GETARG_TRANSACTIONID(0);
+	char	   *result = (char *) palloc(16);
 
-	/* maximum 32 bit unsigned integer representation takes 10 chars */
-	char	   *str = palloc(11);
-
-	snprintf(str, 11, "%lu", (unsigned long) transactionId);
-
-	PG_RETURN_CSTRING(str);
+	snprintf(result, 16, "%lu", (unsigned long) transactionId);
+	PG_RETURN_CSTRING(result);
 }
 
 /*
@@ -148,12 +145,9 @@ xidComparator(const void *arg1, const void *arg2)
 Datum
 cidin(PG_FUNCTION_ARGS)
 {
-	char	   *s = PG_GETARG_CSTRING(0);
-	CommandId	c;
+	char	   *str = PG_GETARG_CSTRING(0);
 
-	c = atoi(s);
-
-	PG_RETURN_COMMANDID(c);
+	PG_RETURN_COMMANDID((CommandId) strtoul(str, NULL, 0));
 }
 
 /*
@@ -165,7 +159,7 @@ cidout(PG_FUNCTION_ARGS)
 	CommandId	c = PG_GETARG_COMMANDID(0);
 	char	   *result = (char *) palloc(16);
 
-	snprintf(result, 16, "%u", (unsigned int) c);
+	snprintf(result, 16, "%lu", (unsigned long) c);
 	PG_RETURN_CSTRING(result);
 }