diff --git a/systest/plugin_test.go b/systest/plugin_test.go
index 3f1edebae99..256c9709fa9 100644
--- a/systest/plugin_test.go
+++ b/systest/plugin_test.go
@@ -135,6 +135,24 @@ func TestPlugins(t *testing.T) {
 		},
 	)
 
+	suite(
+		"word: string @index(anagram) @lang .",
+		`[
+			{ "word@en": "airmen", "word@fr": "no match" },
+			{ "word@en": "no match", "word@fr": "marine" }
+		]`,
+		[]testCase{
+			{`
+				{ q(func: allof(word@en, anagram, "remain")) {
+					word: word@en
+				}}`, `
+				{ "q": [
+					{ "word": "airmen" }
+				]}`,
+			},
+		},
+	)
+
 	suite(
 		"ip: string @index(cidr) .",
 		`[
diff --git a/worker/stringfilter.go b/worker/stringfilter.go
index 7ff0a5b3058..eccc900c068 100644
--- a/worker/stringfilter.go
+++ b/worker/stringfilter.go
@@ -36,6 +36,7 @@ type stringFilter struct {
 	match     matchFunc
 	ineqValue types.Val
 	eqVals    []types.Val
+	tokName   string
 }
 
 func matchStrings(uids *pb.List, values [][]types.Val, filter stringFilter) *pb.List {
@@ -92,15 +93,7 @@ func ineqMatch(value types.Val, filter stringFilter) bool {
 }
 
 func tokenizeValue(value types.Val, filter stringFilter) []string {
-	var tokName string
-	switch filter.funcType {
-	case standardFn:
-		tokName = "term"
-	case fullTextSearchFn:
-		tokName = "fulltext"
-	}
-
-	tokenizer, found := tok.GetTokenizer(tokName)
+	tokenizer, found := tok.GetTokenizer(filter.tokName)
 	// tokenizer was used in previous stages of query processing, it has to be available
 	x.AssertTrue(found)
 
diff --git a/worker/task.go b/worker/task.go
index 0adb18661ea..19a46464021 100644
--- a/worker/task.go
+++ b/worker/task.go
@@ -911,7 +911,8 @@ func needsStringFiltering(srcFn *functionContext, langs []string, attr string) b
 
 	return langForFunc(langs) != "." &&
 		(srcFn.fnType == standardFn || srcFn.fnType == hasFn ||
-			srcFn.fnType == fullTextSearchFn || srcFn.fnType == compareAttrFn)
+			srcFn.fnType == fullTextSearchFn || srcFn.fnType == compareAttrFn ||
+			srcFn.fnType == customIndexFn)
 }
 
 func (qs *queryState) handleCompareScalarFunction(arg funcArgs) error {
@@ -1388,9 +1389,20 @@ func (qs *queryState) filterStringFunction(arg funcArgs) error {
 	case hasFn:
 		// Dont do anything, as filtering based on lang is already
 		// done above.
-	case fullTextSearchFn, standardFn:
+	case fullTextSearchFn:
 		filter.tokens = arg.srcFn.tokens
 		filter.match = defaultMatch
+		filter.tokName = "fulltext"
+		filtered = matchStrings(filtered, values, filter)
+	case standardFn:
+		filter.tokens = arg.srcFn.tokens
+		filter.match = defaultMatch
+		filter.tokName = "term"
+		filtered = matchStrings(filtered, values, filter)
+	case customIndexFn:
+		filter.tokens = arg.srcFn.tokens
+		filter.match = defaultMatch
+		filter.tokName = arg.q.SrcFunc.Args[0]
 		filtered = matchStrings(filtered, values, filter)
 	case compareAttrFn:
 		filter.ineqValue = arg.srcFn.ineqValue