diff --git a/src/main/java/org/mtransit/parser/DefaultAgencyTools.java b/src/main/java/org/mtransit/parser/DefaultAgencyTools.java
index b5bc81b..e767eb4 100644
--- a/src/main/java/org/mtransit/parser/DefaultAgencyTools.java
+++ b/src/main/java/org/mtransit/parser/DefaultAgencyTools.java
@@ -4,7 +4,6 @@
 import org.jetbrains.annotations.Nullable;
 import org.mtransit.commons.CharUtils;
 import org.mtransit.commons.CleanUtils;
-import org.mtransit.commons.CollectionUtils;
 import org.mtransit.commons.CommonsApp;
 import org.mtransit.commons.GTFSCommons;
 import org.mtransit.commons.StringsCleaner;
@@ -31,6 +30,7 @@
 import org.mtransit.parser.mt.MGenerator;
 import org.mtransit.parser.mt.MReader;
 import org.mtransit.parser.mt.data.MAgency;
+import org.mtransit.parser.mt.data.MDirection;
 import org.mtransit.parser.mt.data.MDirectionCardinalType;
 import org.mtransit.parser.mt.data.MRoute;
 import org.mtransit.parser.mt.data.MRouteSNToIDConverter;
@@ -38,7 +38,6 @@
 import org.mtransit.parser.mt.data.MServiceId;
 import org.mtransit.parser.mt.data.MServiceIds;
 import org.mtransit.parser.mt.data.MSpec;
-import org.mtransit.parser.mt.data.MDirection;
 import org.mtransit.parser.mt.data.MString;
 import org.mtransit.parser.mt.data.MStrings;
 import org.mtransit.parser.mt.data.MTripId;
@@ -1855,7 +1854,7 @@ public static HashSet<Integer> getPeriodServiceIds(
 				}
 			}
 		}
-		MTLog.log("[period-service-ids] > Service IDs [%d]: %s.", serviceIdInts.size(), GIDs.toStringPlus(CollectionUtils.sorted(serviceIdInts)));
+		MTLog.log("[period-service-ids] > Service IDs [%d]: %s.", serviceIdInts.size(), GIDs.toStringPlus(serviceIdInts));
 		return serviceIdInts;
 	}
 
diff --git a/src/main/java/org/mtransit/parser/gtfs/data/GIDs.kt b/src/main/java/org/mtransit/parser/gtfs/data/GIDs.kt
index 684299b..6d3a3c9 100644
--- a/src/main/java/org/mtransit/parser/gtfs/data/GIDs.kt
+++ b/src/main/java/org/mtransit/parser/gtfs/data/GIDs.kt
@@ -80,7 +80,7 @@ object GIDs {
     @JvmOverloads
     @JvmStatic
     fun toStringPlus(integers: Iterable<Int?>?, limit: Int = 50): String {
-        return integers?.joinToString(limit = limit) { toStringPlus(it) }?.takeIf { it.isNotBlank() } ?: "{ empty list }"
+        return integers?.map { toStringPlus(it) }?.sorted()?.joinToString(limit = limit) ?: "{ empty list }"
     }
 
     @Suppress("unused")