diff --git a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java
index b0365aa7e19ff28ea126796157e49b0d71b3ba36..b0a1827265e6f04602957f700bd951c37debe5e9 100644
--- a/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java
+++ b/org.eclipse.jgit.junit/src/org/eclipse/jgit/junit/MockSystemReader.java
@@ -244,11 +244,6 @@ public int getTimezone(long when) {
 		return getTimeZone().getOffset(when) / (60 * 1000);
 	}
 
-	@Override
-	public ZoneOffset getTimeZoneAt(Instant when) {
-		return getTimeZoneId().getRules().getOffset(when);
-	}
-
 	@Override
 	public TimeZone getTimeZone() {
 		return TimeZone.getTimeZone("GMT-03:30");
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
index 7150e471bc82a288e28b308aec3587f3f7110963..18b0e152c90e4207c7e29ca20e47aae337444288 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
@@ -178,11 +178,6 @@ public Instant now() {
 		public int getTimezone(long when) {
 			return getTimeZone().getOffset(when) / (60 * 1000);
 		}
-
-		@Override
-		public ZoneOffset getTimeZoneAt(Instant when) {
-			return getTimeZoneId().getRules().getOffset(when);
-		}
 	}
 
 	/**
@@ -569,7 +564,9 @@ public MonotonicClock getClock() {
 	 * @return the local time zone
 	 * @since 7.1
 	 */
-	public abstract ZoneOffset getTimeZoneAt(Instant when);
+	public ZoneOffset getTimeZoneAt(Instant when) {
+		return getTimeZoneId().getRules().getOffset(when);
+	}
 
 	/**
 	 * Get system time zone, possibly mocked for testing