diff --git a/internal/controller/http/v1/sync.go b/internal/controller/http/v1/sync.go
index d3bb83d..09e433d 100644
--- a/internal/controller/http/v1/sync.go
+++ b/internal/controller/http/v1/sync.go
@@ -28,7 +28,7 @@ func (r *syncRoutes) updateProgress(c *gin.Context) {
 	var doc entity.Progress
 	if err := c.ShouldBindJSON(&doc); err != nil {
 		r.l.Error(err)
-		c.JSON(http.StatusBadRequest, gin.H{"message": "Bad request", "code": 4000})
+		c.AsciiJSON(http.StatusBadRequest, gin.H{"message": "Bad request", "code": 4000})
 		return
 	}
 
@@ -36,20 +36,20 @@ func (r *syncRoutes) updateProgress(c *gin.Context) {
 	savedDoc, err := r.progress.Sync(c, doc)
 	if err != nil {
 		r.l.Error(err)
-		c.JSON(http.StatusInternalServerError, gin.H{"message": "Internal server error", "code": 5000})
+		c.AsciiJSON(http.StatusInternalServerError, gin.H{"message": "Internal server error", "code": 5000})
 		return
 	}
 
-	c.JSON(http.StatusOK, gin.H{"timestamp": savedDoc.Timestamp, "document": savedDoc})
+	c.AsciiJSON(http.StatusOK, gin.H{"timestamp": savedDoc.Timestamp, "document": savedDoc})
 }
 
 func (r *syncRoutes) fetchProgress(c *gin.Context) {
 	doc, err := r.progress.Fetch(c, c.Param("document"))
 	if err != nil {
 		r.l.Error(err)
-		c.JSON(http.StatusInternalServerError, gin.H{"message": "Internal server error", "code": 5000})
+		c.AsciiJSON(http.StatusInternalServerError, gin.H{"message": "Internal server error", "code": 5000})
 		return
 	}
 
-	c.JSON(http.StatusOK, doc)
+	c.AsciiJSON(http.StatusOK, doc)
 }
diff --git a/internal/controller/http/v1/users.go b/internal/controller/http/v1/users.go
index aa1df3f..eb70b83 100644
--- a/internal/controller/http/v1/users.go
+++ b/internal/controller/http/v1/users.go
@@ -25,7 +25,7 @@ func newUserRoutes(handler *gin.RouterGroup, a auth.AuthInterface, l logger.Inte
 
 func (r *userRoutes) authenicate(c *gin.Context) {
 	// authenication done by authDeviceMiddleware
-	c.JSON(http.StatusOK, gin.H{"message": "OK", "code": 200})
+	c.AsciiJSON(http.StatusOK, gin.H{"message": "OK", "code": 200})
 }
 
 func authDeviceMiddleware(auth auth.AuthInterface, l logger.Interface) gin.HandlerFunc {
@@ -33,12 +33,12 @@ func authDeviceMiddleware(auth auth.AuthInterface, l logger.Interface) gin.Handl
 		username := c.GetHeader("x-auth-user")
 		hashed_password := c.GetHeader("x-auth-key")
 		if username == "" || hashed_password == "" {
-			c.JSON(http.StatusUnauthorized, gin.H{"message": "Unauthorized", "code": 2001})
+			c.AsciiJSON(http.StatusUnauthorized, gin.H{"message": "Unauthorized", "code": 2001})
 			c.Abort()
 			return
 		}
 		if !auth.CheckDevicePassword(c.Request.Context(), username, hashed_password, false) {
-			c.JSON(http.StatusUnauthorized, gin.H{"message": "Unauthorized", "code": 2001})
+			c.AsciiJSON(http.StatusUnauthorized, gin.H{"message": "Unauthorized", "code": 2001})
 			c.Abort()
 			return
 		}