diff --git a/changelog/65_UNRELEASED_xxxx-xx-xx.md b/changelog/65_UNRELEASED_xxxx-xx-xx.md
index 09ecd6f3..70ba5879 100644
--- a/changelog/65_UNRELEASED_xxxx-xx-xx.md
+++ b/changelog/65_UNRELEASED_xxxx-xx-xx.md
@@ -5,3 +5,6 @@
 - Fixed that the labels of context-/more-menu items were not readable in Night Mode (thanks @corbolais)
 - Fixed that auto night mode over midnight did not always work
 - Fixed that the "Add as new product" productpicker workflow, started from the shopping list item form, always selected the default shopping list after finishing the flow
+
+### API
+- Fixed that backslashes were not allowed in API query filters
diff --git a/controllers/BaseApiController.php b/controllers/BaseApiController.php
index 0943835a..56714c91 100644
--- a/controllers/BaseApiController.php
+++ b/controllers/BaseApiController.php
@@ -10,7 +10,7 @@ class BaseApiController extends BaseController
 
 	const PATTERN_OPERATOR = '!?(=|~|<|>|(>=)|(<=)|(§))';
 
-	const PATTERN_VALUE = '[A-Za-z\p{L}\p{M}*_0-9.$#^| -]+';
+	const PATTERN_VALUE = '[A-Za-z\p{L}\p{M}0-9*_.$#^| -\\\]+';
 
 	protected $OpenApiSpec = null;