diff --git a/includes/AbuseFilterRunner.php b/includes/AbuseFilterRunner.php
index 6106d5790..a5e017d82 100644
--- a/includes/AbuseFilterRunner.php
+++ b/includes/AbuseFilterRunner.php
@@ -728,7 +728,7 @@ class AbuseFilterRunner {
 				}
 
 				$currentExpiry = SpecialBlock::parseExpiryInput( $expiry );
-				if ( $currentExpiry > SpecialBlock::parseExpiryInput( $maxExpiry ) ) {
+				if ( $maxExpiry === -1 || $currentExpiry > SpecialBlock::parseExpiryInput( $maxExpiry ) ) {
 					// Save the parameters to issue the block with
 					$maxExpiry = $expiry;
 					$blockValues = [