diff --git a/includes/parser/AbuseFilterCachingParser.php b/includes/parser/AbuseFilterCachingParser.php
index 40bfb0572..27bf96fe0 100644
--- a/includes/parser/AbuseFilterCachingParser.php
+++ b/includes/parser/AbuseFilterCachingParser.php
@@ -171,6 +171,9 @@ class AbuseFilterCachingParser extends AbuseFilterParser {
 				list( $array, $offset ) = $node->children;
 
 				$array = $this->evalNode( $array );
+				// Note: we MUST evaluate the offset to ensure it is valid, regardless
+				// of $array!
+				$offset = $this->evalNode( $offset )->toInt();
 
 				if ( $array->getType() === AFPData::DUNDEFINED ) {
 					return new AFPData( AFPData::DUNDEFINED );
@@ -180,8 +183,6 @@ class AbuseFilterCachingParser extends AbuseFilterParser {
 					throw new AFPUserVisibleException( 'notarray', $node->position, [] );
 				}
 
-				$offset = $this->evalNode( $offset )->toInt();
-
 				$array = $array->toArray();
 				if ( count( $array ) <= $offset ) {
 					throw new AFPUserVisibleException( 'outofbounds', $node->position,
diff --git a/tests/phpunit/unit/AbuseFilterParserTest.php b/tests/phpunit/unit/AbuseFilterParserTest.php
index c4dd1343d..072893821 100644
--- a/tests/phpunit/unit/AbuseFilterParserTest.php
+++ b/tests/phpunit/unit/AbuseFilterParserTest.php
@@ -301,6 +301,8 @@ class AbuseFilterParserTest extends AbuseFilterParserTestCase {
 			[ 'a[1] := 5', 'getVarValue' ],
 			[ 'a[] := 5', 'getVarValue' ],
 			[ 'a = 5', 'getVarValue' ],
+			[ 'timestamp[a]', 'getVarValue' ],
+			[ 'x := []; x[a] := 1', 'getVarValue' ],
 		];
 	}