diff --git a/docs/office.md b/docs/office.md
index 1ca8edc0c59..c63f7219e91 100644
--- a/docs/office.md
+++ b/docs/office.md
@@ -121,7 +121,7 @@ Content-Type: application/vnd.api+json
 }
 ```
 
-### GET /office/keys/:key
+### POST /office/keys/:key
 
 If a document is being edited while a new version is uploaded (via the desktop
 for example), the OO webapp should call this endpoint if the user chooses to
@@ -131,7 +131,7 @@ created, so that no work is lost.
 #### Request
 
 ```http
-GET /office/keys/7c7ccc2e7137ba774b7e44de HTTP/1.1
+POST /office/keys/7c7ccc2e7137ba774b7e44de HTTP/1.1
 Host: bob.cozy.example
 ```
 
diff --git a/model/office/file_by_key.go b/model/office/file_by_key.go
index e10801bff69..71932522924 100644
--- a/model/office/file_by_key.go
+++ b/model/office/file_by_key.go
@@ -7,7 +7,12 @@ import (
 	"github.com/cozy/cozy-stack/model/vfs"
 )
 
-func GetFileByKey(inst *instance.Instance, key string) (*vfs.FileDoc, error) {
+// EnsureFileForKey returns the file that will be written when OnlyOffice will
+// save a document with the given key. The general case is that is the file
+// that has been opened. But, it can also be a new file if a conflict has
+// happened because a new version has been uploaded for this file (by the
+// desktop client for example).
+func EnsureFileForKey(inst *instance.Instance, key string) (*vfs.FileDoc, error) {
 	detector, err := GetStore().GetDoc(inst, key)
 	if err != nil {
 		return nil, err
diff --git a/web/office/office.go b/web/office/office.go
index 2ae6bfba466..08081c67434 100644
--- a/web/office/office.go
+++ b/web/office/office.go
@@ -61,9 +61,9 @@ func Open(c echo.Context) error {
 	return jsonapi.Data(c, http.StatusOK, doc, nil)
 }
 
-func GetFileByKey(c echo.Context) error {
+func FileByKey(c echo.Context) error {
 	inst := middlewares.GetInstance(c)
-	file, err := office.GetFileByKey(inst, c.Param("key"))
+	file, err := office.EnsureFileForKey(inst, c.Param("key"))
 	if err != nil {
 		return wrapError(err)
 	}
@@ -102,7 +102,7 @@ func Callback(c echo.Context) error {
 // Routes sets the routing for the collaborative edition of office documents.
 func Routes(router *echo.Group) {
 	router.GET("/:id/open", Open)
-	router.GET("/keys/:key", GetFileByKey)
+	router.POST("/keys/:key", FileByKey)
 	router.POST("/callback", Callback)
 }
 
diff --git a/web/office/office_test.go b/web/office/office_test.go
index 61a10143cb5..19375b3ecfa 100644
--- a/web/office/office_test.go
+++ b/web/office/office_test.go
@@ -145,7 +145,7 @@ func TestOffice(t *testing.T) {
 		key = document.Value("key").String().NotEmpty().Raw()
 
 		// the key is associated to this file
-		obj = e.GET("/office/keys/"+key).
+		obj = e.POST("/office/keys/"+key).
 			WithHeader("Authorization", "Bearer "+token).
 			Expect().Status(200).
 			JSON(httpexpect.ContentOpts{MediaType: "application/vnd.api+json"}).
@@ -160,7 +160,7 @@ func TestOffice(t *testing.T) {
 		// When an upload is made that changes the content of this document,
 		// the key will now be associated to a conflict file
 		updateFile(t, inst, fileID)
-		obj = e.GET("/office/keys/"+key).
+		obj = e.POST("/office/keys/"+key).
 			WithHeader("Authorization", "Bearer "+token).
 			Expect().Status(200).
 			JSON(httpexpect.ContentOpts{MediaType: "application/vnd.api+json"}).
@@ -175,7 +175,7 @@ func TestOffice(t *testing.T) {
 		assert.Equal(t, "letter (2).docx", conflictName)
 
 		// When another user uses the same key, they obtains the same file
-		obj = e.GET("/office/keys/"+key).
+		obj = e.POST("/office/keys/"+key).
 			WithHeader("Authorization", "Bearer "+token).
 			Expect().Status(200).
 			JSON(httpexpect.ContentOpts{MediaType: "application/vnd.api+json"}).