diff --git a/gerrit-server/src/test/java/com/google/gerrit/testutil/TestTimeUtil.java b/gerrit-server/src/test/java/com/google/gerrit/testutil/TestTimeUtil.java
index dd44cb9ae5..792120484f 100644
--- a/gerrit-server/src/test/java/com/google/gerrit/testutil/TestTimeUtil.java
+++ b/gerrit-server/src/test/java/com/google/gerrit/testutil/TestTimeUtil.java
@@ -20,6 +20,10 @@ import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import java.sql.Timestamp;
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.atomic.AtomicLong;
+import org.eclipse.jgit.lib.Config;
+import org.eclipse.jgit.storage.file.FileBasedConfig;
+import org.eclipse.jgit.util.FS;
+import org.eclipse.jgit.util.SystemReader;
 import org.joda.time.DateTime;
 import org.joda.time.DateTimeUtils;
 import org.joda.time.DateTimeUtils.MillisProvider;
@@ -56,6 +60,7 @@ public class TestTimeUtil {
   public static synchronized void setClockStep(long clockStep, TimeUnit clockStepUnit) {
     checkState(clockMs != null, "call resetWithClockStep first");
     clockStepMs = MILLISECONDS.convert(clockStep, clockStepUnit);
+
     DateTimeUtils.setCurrentMillisProvider(
         new MillisProvider() {
           @Override
@@ -63,6 +68,47 @@ public class TestTimeUtil {
             return clockMs.getAndAdd(clockStepMs);
           }
         });
+
+    SystemReader.setInstance(null);
+    final SystemReader defaultReader = SystemReader.getInstance();
+    SystemReader r =
+        new SystemReader() {
+          @Override
+          public String getHostname() {
+            return defaultReader.getHostname();
+          }
+
+          @Override
+          public String getenv(String variable) {
+            return defaultReader.getenv(variable);
+          }
+
+          @Override
+          public String getProperty(String key) {
+            return defaultReader.getProperty(key);
+          }
+
+          @Override
+          public FileBasedConfig openUserConfig(Config parent, FS fs) {
+            return defaultReader.openUserConfig(parent, fs);
+          }
+
+          @Override
+          public FileBasedConfig openSystemConfig(Config parent, FS fs) {
+            return defaultReader.openSystemConfig(parent, fs);
+          }
+
+          @Override
+          public long getCurrentTime() {
+            return clockMs.getAndAdd(clockStepMs);
+          }
+
+          @Override
+          public int getTimezone(long when) {
+            return defaultReader.getTimezone(when);
+          }
+        };
+    SystemReader.setInstance(r);
   }
 
   /**
@@ -86,10 +132,15 @@ public class TestTimeUtil {
     clockMs.addAndGet(clockStepUnit.toMillis(clockStep));
   }
 
-  /** Reset the clock to use the actual system clock. */
+  /**
+   * Reset the clock to use the actual system clock.
+   *
+   * <p>As a side effect, resets the {@link SystemReader} to the original default instance.
+   */
   public static synchronized void useSystemTime() {
     clockMs = null;
     DateTimeUtils.setCurrentMillisSystem();
+    SystemReader.setInstance(null);
   }
 
   private TestTimeUtil() {}