diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java
index 7aa65e8..e8a621b 100644
--- a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Device.java
@@ -30,7 +30,7 @@ public abstract class Device {
      * The room this device belongs in, as a foreign key id. To use when updating and inserting from
      * a REST call.
      */
-    @Column(name = "room_id", nullable = false)
+    @Column(name = "room_id", nullable = false, unique = true)
     @NotNull
     private Long roomId;
 
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/KnobDimmer.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/KnobDimmer.java
index 0a90998..7f4056b 100644
--- a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/KnobDimmer.java
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/KnobDimmer.java
@@ -33,7 +33,11 @@ public class KnobDimmer extends Dimmer {
                 dl.setIntensity((dl.getIntensity() + 5) % 105);
             } else {
                 dl.setIntensity(dl.getIntensity() + (5 - remainder));
-                dl.setIntensity((dl.getIntensity() - 5) % 105);
+                if (dl.getIntensity() == 0) {
+                    dl.setIntensity(100);
+                } else {
+                    dl.setIntensity(dl.getIntensity() - 5);
+                }
             }
         }
     }
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java
index e15805b..f6edfd3 100644
--- a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/Room.java
@@ -10,7 +10,7 @@ public class Room {
 
     @Id
     @GeneratedValue(strategy = GenerationType.AUTO)
-    @Column(name = "id", updatable = false, nullable = false)
+    @Column(name = "id", updatable = false, nullable = false, unique = true)
     @ApiModelProperty(hidden = true)
     private Long id;
 
@@ -33,7 +33,7 @@ public class Room {
      * inserting from a REST call.
      */
     @NotNull
-    @Column(name = "user_id", nullable = false)
+    @Column(name = "user_id", nullable = false, unique = true)
     private Long userId;
 
     /** The user given name of this room (e.g. 'Master bedroom') */
diff --git a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/User.java b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/User.java
index 67f95d4..e33b130 100644
--- a/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/User.java
+++ b/src/main/java/ch/usi/inf/sa4/sanmarinoes/smarthut/models/User.java
@@ -14,7 +14,7 @@ public class User {
 
     @Id
     @GeneratedValue(strategy = GenerationType.AUTO)
-    @Column(name = "id", updatable = false, nullable = false)
+    @Column(name = "id", updatable = false, nullable = false, unique = true)
     @ApiModelProperty(hidden = true)
     private Long id;
 
@@ -24,9 +24,9 @@ public class User {
     @NotEmpty(message = "Please provide a full name")
     private String name;
 
-    /** The full name of the user */
+    /** The full username of the user */
     @NotNull
-    @Column(nullable = false)
+    @Column(nullable = false, unique = true)
     @NotEmpty(message = "Please provide a username")
     private String username;