diff --git a/modules/reitit-malli/src/reitit/coercion/malli.cljc b/modules/reitit-malli/src/reitit/coercion/malli.cljc
index 0f14ab7f..813bbc20 100644
--- a/modules/reitit-malli/src/reitit/coercion/malli.cljc
+++ b/modules/reitit-malli/src/reitit/coercion/malli.cljc
@@ -9,7 +9,8 @@
             [malli.swagger :as swagger]
             [malli.transform :as mt]
             [malli.util :as mu]
-            [reitit.coercion :as coercion]))
+            [reitit.coercion :as coercion]
+            [clojure.string :as string]))
 
 ;;
 ;; coercion
@@ -79,11 +80,13 @@
 (defn- -query-string-coercer
   "Create coercer for query-parameters, always allows extra params and does
   encoding using string-transformer."
-  [schema transfomers options]
+  [schema string-transformer-provider options]
   (let [;; Always allow extra paramaters on query-parameters encoding
         open-schema (mu/open-schema schema)
         ;; Do not remove extra keys
-        string-transformer (-transformer string-transformer-provider (assoc options :strip-extra-keys false))
+        string-transformer (if (satisfies? TransformationProvider string-transformer-provider)
+                             (-transformer string-transformer-provider (assoc options :strip-extra-keys false))
+                             string-transformer-provider)
         encoder (m/encoder open-schema options string-transformer)]
     (fn [value format]
       (if encoder
@@ -126,6 +129,9 @@
   ([opts]
    (let [{:keys [transformers lite compile options error-keys encode-error] :as opts} (merge default-options opts)
          show? (fn [key] (contains? error-keys key))
+         ;; Query-string-coercer needs to construct transfomer without strip-extra-keys so it will
+         ;; use the transformer-provider directly.
+         string-transformer-provider (:default (:string transformers))
          transformers (walk/prewalk #(if (satisfies? TransformationProvider %) (-transformer % opts) %) transformers)
          compile (if lite (fn [schema options]
                             (compile (binding [l/*options* options] (l/schema schema)) options))
@@ -192,6 +198,6 @@
        (-response-coercer [_ schema]
          (-coercer schema :response transformers :encode opts))
        (-query-string-coercer [_ schema]
-         (-query-string-coercer schema transformers opts))))))
+         (-query-string-coercer schema string-transformer-provider opts))))))
 
 (def coercion (create default-options))
diff --git a/test/cljs/reitit/frontend/core_test.cljs b/test/cljs/reitit/frontend/core_test.cljs
index c99fba12..3bb7907f 100644
--- a/test/cljs/reitit/frontend/core_test.cljs
+++ b/test/cljs/reitit/frontend/core_test.cljs
@@ -1,6 +1,8 @@
 (ns reitit.frontend.core-test
   (:require [clojure.string :as str]
             [clojure.test :refer [are deftest is testing]]
+            [malli.core :as m]
+            [malli.transform :as mt]
             [reitit.coercion :as rc]
             [reitit.coercion.malli :as rcm]
             [reitit.coercion.schema :as rcs]
@@ -305,11 +307,26 @@
           (rf/match->path {:path "foo"} {:q :x})
           "foo?q=x")))
 
-  (is (= "foo?q=__x"
-         (rf/match->path {:data {:coercion rcm/coercion
-                                 :parameters {:query [[:map
-                                                       [:q {:decode/string (fn [s] (keyword (subs s 2)))
-                                                            :encode/string (fn [k] (str "__" (name k)))}
-                                                        :keyword]]]}}
-                          :path "foo"}
-                         {:q "x"}))))
+  (testing "default string transformer"
+    (is (= "foo?q=__x"
+           (rf/match->path {:data {:coercion rcm/coercion
+                                   :parameters {:query [[:map
+                                                         [:q {:decode/string (fn [s] (keyword (subs s 2)))
+                                                              :encode/string (fn [k] (str "__" (name k)))}
+                                                          :keyword]]]}}
+                            :path "foo"}
+                           {:q "x"}))))
+
+  (testing "custom string transformer"
+    (is (= "foo?q=--x"
+           (rf/match->path {:data {:coercion (rcm/create (assoc-in rcm/default-options
+                                                                   [:transformers :string :default]
+                                                                   (mt/transformer
+                                                                     {:name :foo-string
+                                                                      :encoders {:foo/type {:leave (fn [x] (str "--" x))}}})))
+                                   :parameters {:query [[:map
+                                                         [:q (m/-simple-schema
+                                                               {:type :foo/type
+                                                                :pred string?})]]]}}
+                            :path "foo"}
+                           {:q "x"})))))