diff --git a/api/src/main/java/com/emnify/sdk/model/Sim.java b/api/src/main/java/com/emnify/sdk/model/Sim.java
index 21aa989..5da6b2c 100644
--- a/api/src/main/java/com/emnify/sdk/model/Sim.java
+++ b/api/src/main/java/com/emnify/sdk/model/Sim.java
@@ -53,6 +53,10 @@ public class Sim {
   @SerializedName(SERIALIZED_NAME_IMSI)
   private String imsi;
 
+  public static final String SERIALIZED_NAME_ACTIVATE = "activate";
+  @SerializedName(SERIALIZED_NAME_ACTIVATE)
+  private Boolean activate;
+
 
   public Sim id(Integer id) {
     
@@ -145,6 +149,29 @@ public void setImsi(String imsi) {
   }
 
 
+  public Sim activate(Boolean activate) {
+
+    this.activate = activate;
+    return this;
+  }
+
+   /**
+   * Whether the SIM is activated when it is assigned to the endpoint. Defaults to true server-side, so pass false to assign the SIM without activating it. Left null the property is omitted from the request.
+   * @return activate
+  **/
+  @javax.annotation.Nullable
+  @ApiModelProperty(value = "Whether the SIM is activated when it is assigned to the endpoint. Defaults to true server-side, so pass false to assign the SIM without activating it.")
+
+  public Boolean getActivate() {
+    return activate;
+  }
+
+
+  public void setActivate(Boolean activate) {
+    this.activate = activate;
+  }
+
+
   @Override
   public boolean equals(Object o) {
     if (this == o) {
@@ -157,12 +184,13 @@ public boolean equals(Object o) {
     return Objects.equals(this.id, sim.id) &&
         Objects.equals(this.iccid, sim.iccid) &&
         Objects.equals(this.msisdn, sim.msisdn) &&
-        Objects.equals(this.imsi, sim.imsi);
+        Objects.equals(this.imsi, sim.imsi) &&
+        Objects.equals(this.activate, sim.activate);
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(id, iccid, msisdn, imsi);
+    return Objects.hash(id, iccid, msisdn, imsi, activate);
   }
 
   @Override
@@ -173,6 +201,7 @@ public String toString() {
     sb.append("    iccid: ").append(toIndentedString(iccid)).append("\n");
     sb.append("    msisdn: ").append(toIndentedString(msisdn)).append("\n");
     sb.append("    imsi: ").append(toIndentedString(imsi)).append("\n");
+    sb.append("    activate: ").append(toIndentedString(activate)).append("\n");
     sb.append("}");
     return sb.toString();
   }
diff --git a/api/src/test/java/com/emnify/sdk/model/SimTest.java b/api/src/test/java/com/emnify/sdk/model/SimTest.java
index 11ef114..3990fd1 100644
--- a/api/src/test/java/com/emnify/sdk/model/SimTest.java
+++ b/api/src/test/java/com/emnify/sdk/model/SimTest.java
@@ -21,6 +21,8 @@
 
 package com.emnify.sdk.model;
 
+import com.emnify.sdk.JSON;
+import com.google.gson.Gson;
 import com.google.gson.TypeAdapter;
 import com.google.gson.annotations.JsonAdapter;
 import com.google.gson.annotations.SerializedName;
@@ -80,4 +82,23 @@ public void imsiTest() {
         // TODO: test imsi
     }
 
+    /**
+     * Test that the property 'activate' reaches the request body.
+     *
+     * The API activates an assigned SIM by default, so a client that cannot
+     * send activate=false cannot assign a SIM without activating (and billing)
+     * it. Serialization goes through the same Gson instance ApiClient uses.
+     */
+    @Test
+    public void activateIsSerializedTest() {
+        Gson gson = JSON.createGson().create();
+
+        Assert.assertEquals("{\"id\":250,\"activate\":false}",
+                gson.toJson(new Sim().id(250).activate(false)));
+        Assert.assertEquals("{\"id\":250,\"activate\":true}",
+                gson.toJson(new Sim().id(250).activate(true)));
+        // left unset the property is omitted, so the API default applies
+        Assert.assertEquals("{\"id\":250}", gson.toJson(new Sim().id(250)));
+    }
+
 }