diff --git a/commafeed-server/src/main/java/com/commafeed/backend/favicon/Favicon.java b/commafeed-server/src/main/java/com/commafeed/backend/favicon/Favicon.java
index 4e2ea9e5..67f6daa7 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/favicon/Favicon.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/favicon/Favicon.java
@@ -17,7 +17,7 @@ public record Favicon(byte[] icon, MediaType mediaType) {
 		try {
 			return MediaType.valueOf(contentType);
 		} catch (Exception e) {
-			log.debug("invalid content type '{}' received, returning default value", contentType);
+			log.debug("invalid content type '{}' received, returning default value", contentType, e);
 			return DEFAULT_MEDIA_TYPE;
 		}
 	}
diff --git a/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshEngine.java b/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshEngine.java
index 43d593f3..6c3b52c1 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshEngine.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/feed/FeedRefreshEngine.java
@@ -164,9 +164,11 @@ public class FeedRefreshEngine {
 			Instant lastLoginThreshold = config.feedRefresh().userInactivityPeriod().isZero() ? null
 					: Instant.now().minus(config.feedRefresh().userInactivityPeriod());
 			List<Feed> feeds = feedDAO.findNextUpdatable(max, lastLoginThreshold);
-			// update disabledUntil to prevent feeds from being returned again by feedDAO.findNextUpdatable()
-			Instant nextUpdateDate = Instant.now().plus(config.feedRefresh().interval());
-			feedDAO.setDisabledUntil(feeds.stream().map(AbstractModel::getId).toList(), nextUpdateDate);
+			if (!feeds.isEmpty()) {
+				// update disabledUntil to prevent feeds from being returned again by feedDAO.findNextUpdatable()
+				Instant nextUpdateDate = Instant.now().plus(config.feedRefresh().interval());
+				feedDAO.setDisabledUntil(feeds.stream().map(AbstractModel::getId).toList(), nextUpdateDate);
+			}
 			return feeds;
 		});
 	}
diff --git a/commafeed-server/src/main/java/com/commafeed/backend/opml/OPMLImporter.java b/commafeed-server/src/main/java/com/commafeed/backend/opml/OPMLImporter.java
index dd4b08d2..ac575c5b 100644
--- a/commafeed-server/src/main/java/com/commafeed/backend/opml/OPMLImporter.java
+++ b/commafeed-server/src/main/java/com/commafeed/backend/opml/OPMLImporter.java
@@ -30,7 +30,11 @@ public class OPMLImporter {
 	private final FeedSubscriptionService feedSubscriptionService;
 
 	public void importOpml(User user, String xml) throws IllegalArgumentException, FeedException {
-		xml = xml.substring(xml.indexOf('<'));
+		int index = xml.indexOf('<');
+		if (index == -1) {
+			throw new IllegalArgumentException("Invalid OPML: no start tag found");
+		}
+		xml = xml.substring(index);
 		WireFeedInput input = new WireFeedInput();
 		Opml feed = (Opml) input.build(new StringReader(xml));
 		List<Outline> outlines = feed.getOutlines();
diff --git a/commafeed-server/src/main/java/com/commafeed/frontend/resource/CategoryREST.java b/commafeed-server/src/main/java/com/commafeed/frontend/resource/CategoryREST.java
index 93ce753b..c8592628 100644
--- a/commafeed-server/src/main/java/com/commafeed/frontend/resource/CategoryREST.java
+++ b/commafeed-server/src/main/java/com/commafeed/frontend/resource/CategoryREST.java
@@ -337,7 +337,7 @@ public class CategoryREST {
 		}
 
 		FeedCategory parent = null;
-		if (req.getParentId() != null && !CategoryREST.ALL.equals(req.getParentId())
+		if (req.getParentId() != null && !ALL.equals(req.getParentId())
 				&& !Strings.CS.equals(req.getParentId(), String.valueOf(req.getId()))) {
 			parent = feedCategoryDAO.findById(user, Long.valueOf(req.getParentId()));
 		}
diff --git a/commafeed-server/src/main/java/com/commafeed/frontend/resource/FeedREST.java b/commafeed-server/src/main/java/com/commafeed/frontend/resource/FeedREST.java
index 9e857c4f..b156f111 100644
--- a/commafeed-server/src/main/java/com/commafeed/frontend/resource/FeedREST.java
+++ b/commafeed-server/src/main/java/com/commafeed/frontend/resource/FeedREST.java
@@ -181,7 +181,7 @@ public class FeedREST {
 			boolean hasMore = entries.getEntries().size() > limit;
 			if (hasMore) {
 				entries.setHasMore(true);
-				entries.getEntries().remove(entries.getEntries().size() - 1);
+				entries.getEntries().removeLast();
 			}
 		} else {
 			return Response.status(Status.NOT_FOUND).entity("<message>feed not found</message>").build();