diff --git a/src/java/davmail/exchange/ExchangeSession.java b/src/java/davmail/exchange/ExchangeSession.java
index 814a8bc5..4ee0cc9b 100644
--- a/src/java/davmail/exchange/ExchangeSession.java
+++ b/src/java/davmail/exchange/ExchangeSession.java
@@ -2591,9 +2591,11 @@ public abstract class ExchangeSession {
                                 return false;
                             }
                         });
-                        for (File file : oldestFiles) {
-                            if (!file.delete()) {
-                                LOGGER.warn("Unable to delete " + file.getAbsolutePath());
+                        if (oldestFiles != null) {
+                            for (File file : oldestFiles) {
+                                if (!file.delete()) {
+                                    LOGGER.warn("Unable to delete " + file.getAbsolutePath());
+                                }
                             }
                         }
                     } catch (Exception ex) {