diff --git a/php/servers/servers-rooms.php b/php/servers/servers-rooms.php
index fafbddf..963fbb0 100644
--- a/php/servers/servers-rooms.php
+++ b/php/servers/servers-rooms.php
@@ -1640,7 +1640,7 @@
 				$pubkey_old = $this->get_pubkey();
 				$pubkey_new = url_get_pubkey($link);
 				log_error(
-					"Key collision for $base_url:" .
+					"Key mismatch for $base_url:" .
 					"Have $pubkey_old, fetched $pubkey_new from $preview_url"
 				);
 				return false;
diff --git a/php/servers/sources.php b/php/servers/sources.php
index bf6b9a9..2bfcbf7 100644
--- a/php/servers/sources.php
+++ b/php/servers/sources.php
@@ -49,7 +49,8 @@
 		private static function sdir_validate_entry(
 			array $room_entry,
 			bool &$missing_url,
-			bool &$missing_tags
+			bool &$missing_tags,
+			bool &$invalid_url
 		): bool {
 			if (!isset($room_entry['url']) || !is_string($room_entry['url'])) {
 				log_value($room_entry);
@@ -63,10 +64,16 @@
 				return false;
 			}
 
+			if (!filter_var($room_entry['url'], FILTER_VALIDATE_URL)) {
+				log_value($room_entry);
+				$invalid_url = true;
+				return false;
+			}
+
 			return true;
 		}
 
-		private static function sdir_report_errors(bool $entry_missing_url, bool $entry_missing_tags) {
+		private static function sdir_report_errors(bool $entry_missing_url, bool $entry_missing_tags, bool $entry_invalid_url) {
 			if ($entry_missing_url) {
 				log_error("One or more room entries from session.directory is missing the 'url' parameter.");
 			}
@@ -74,6 +81,10 @@
 			if ($entry_missing_tags) {
 				log_error("One or more room entries from session.directory is missing the 'tags' parameter.");
 			}
+
+			if ($entry_invalid_url) {
+				log_warning("One or more room entries from session.directory contain an invalid 'url' parameter.");
+			}
 		}
 
 		private function get_sdir_entries(): array|bool {
@@ -97,7 +108,7 @@
 
 			foreach ($rooms as $room_entry) {
 				if (!SDIRCommunitySource::sdir_validate_entry(
-					$room_entry, $entry_missing_url, $entry_missing_tags
+					$room_entry, $entry_missing_url, $entry_missing_tags, $entry_invalid_url
 				)) {
 					continue;
 				}
@@ -116,7 +127,7 @@
 				}
 			}
 
-			SDIRCommunitySource::sdir_report_errors($entry_missing_url, $entry_missing_tags);
+			SDIRCommunitySource::sdir_report_errors($entry_missing_url, $entry_missing_tags, $entry_invalid_url);
 
 			return true;
 		}
diff --git a/php/utils/utils.php b/php/utils/utils.php
index d01b201..6178e7d 100644
--- a/php/utils/utils.php
+++ b/php/utils/utils.php
@@ -130,11 +130,16 @@
 	/**
 	 * Extracts the server public key from a join URL.
 	 * @param string $join_url Join URL for Session Community.
-	 * @return string SOGS public key
+	 * @return string|null SOGS public key
 	 */
 	function url_get_pubkey(string $join_url) {
 		$url_components = parse_url($join_url);
-		parse_str($url_components['query'], $query_components);
+		$query = $url_components['query'] ?? "";
+		if ($query === "") {
+			log_value($join_url);
+			throw new DomainException("Join URL does not contain public key");
+		}
+		parse_str($query, $query_components);
 		return $query_components['public_key'];
 	}