diff --git a/azurerm/resource_arm_virtual_machine_scale_set.go b/azurerm/resource_arm_virtual_machine_scale_set.go
index 005d0691eede..ef42ea143ac7 100644
--- a/azurerm/resource_arm_virtual_machine_scale_set.go
+++ b/azurerm/resource_arm_virtual_machine_scale_set.go
@@ -396,7 +396,7 @@ func resourceArmVirtualMachineScaleSet() *schema.Resource {
 
 									"primary": {
 										Type:     schema.TypeBool,
-										Optional: true,
+										Required: true,
 									},
 
 									"public_ip_address_configuration": {
@@ -1480,6 +1480,7 @@ func expandAzureRmVirtualMachineScaleSetNetworkProfile(d *schema.ResourceData) *
 		for _, ipConfigConfig := range ipConfigurationConfigs {
 			ipconfig := ipConfigConfig.(map[string]interface{})
 			name := ipconfig["name"].(string)
+			primary := ipconfig["primary"].(bool)
 			subnetId := ipconfig["subnet_id"].(string)
 
 			ipConfiguration := compute.VirtualMachineScaleSetIPConfiguration{
@@ -1491,6 +1492,8 @@ func expandAzureRmVirtualMachineScaleSetNetworkProfile(d *schema.ResourceData) *
 				},
 			}
 
+			ipConfiguration.Primary = &primary
+
 			if v := ipconfig["application_gateway_backend_address_pool_ids"]; v != nil {
 				pools := v.(*schema.Set).List()
 				resources := make([]compute.SubResource, 0, len(pools))
@@ -1527,11 +1530,6 @@ func expandAzureRmVirtualMachineScaleSetNetworkProfile(d *schema.ResourceData) *
 				ipConfiguration.LoadBalancerInboundNatPools = &rulesResources
 			}
 
-			if v := ipconfig["primary"]; v != nil {
-				primary := v.(bool)
-				ipConfiguration.Primary = &primary
-			}
-
 			if v := ipconfig["public_ip_address_configuration"]; v != nil {
 				publicIpConfigs := v.([]interface{})
 				for _, publicIpConfigConfig := range publicIpConfigs {
diff --git a/azurerm/resource_arm_virtual_machine_scale_set_test.go b/azurerm/resource_arm_virtual_machine_scale_set_test.go
index 624279c753e9..f0fe0ef05d3d 100644
--- a/azurerm/resource_arm_virtual_machine_scale_set_test.go
+++ b/azurerm/resource_arm_virtual_machine_scale_set_test.go
@@ -1164,6 +1164,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1249,6 +1250,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1424,6 +1426,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 			accelerated_networking = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1509,6 +1512,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 	  ip_forwarding = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1596,6 +1600,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 	  }
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1684,6 +1689,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1874,6 +1880,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -1959,6 +1966,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -2070,6 +2078,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
     primary = true
     ip_configuration {
       name                                   = "TestIPConfiguration"
+      primary                                = true
       subnet_id                              = "${azurerm_subnet.test.id}"
       load_balancer_backend_address_pool_ids = ["${azurerm_lb_backend_address_pool.test.id}"]
     }
@@ -2183,6 +2192,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
     primary = true
     ip_configuration {
       name                                   = "TestIPConfiguration"
+      primary                                = true
       subnet_id                              = "${azurerm_subnet.test.id}"
       load_balancer_backend_address_pool_ids = ["${azurerm_lb_backend_address_pool.test.id}"]
     }
@@ -2301,6 +2311,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
     primary = true
     ip_configuration {
       name                                   = "TestIPConfiguration"
+      primary                                = true
       subnet_id                              = "${azurerm_subnet.test.id}"
       load_balancer_backend_address_pool_ids = ["${azurerm_lb_backend_address_pool.test.id}"]
     }
@@ -2368,6 +2379,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
     primary = true
     ip_configuration {
       name = "TestIPConfiguration"
+      primary = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -2434,6 +2446,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
         primary = true
         ip_configuration {
             name = "TestIPConfiguration"
+            primary = true
             subnet_id = "${azurerm_subnet.test.id}"
         }
     }
@@ -2517,6 +2530,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
     primary = true
     ip_configuration {
       name = "TestIPConfiguration"
+      primary = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -2582,6 +2596,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
     primary = true
     ip_configuration {
       name = "TestIPConfiguration"
+      primary = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -2662,6 +2677,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name                                         = "TestIPConfiguration"
+      primary                                      = true
       subnet_id                                    = "${azurerm_subnet.test.id}"
       application_gateway_backend_address_pool_ids = ["${azurerm_application_gateway.test.backend_address_pool.0.id}"]
     }
@@ -2887,6 +2903,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name                                   = "TestIPConfiguration"
+      primary                                = true
       subnet_id                              = "${azurerm_subnet.test.id}"
       load_balancer_backend_address_pool_ids = ["${azurerm_lb_backend_address_pool.test.id}"]
       load_balancer_inbound_nat_rules_ids    = ["${azurerm_lb_nat_pool.test.id}"]
@@ -2972,6 +2989,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3056,6 +3074,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3151,6 +3170,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3254,6 +3274,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3345,6 +3366,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3456,6 +3478,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3560,6 +3583,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3656,6 +3680,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3742,6 +3767,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name                                   = "TestIPConfiguration"
+      primary                                = true
       subnet_id                              = "${azurerm_subnet.test.id}"
       load_balancer_backend_address_pool_ids = ["${azurerm_lb_backend_address_pool.test.id}"]
     }
@@ -3837,6 +3863,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -3902,6 +3929,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+      primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -4073,6 +4101,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "TestIPConfiguration"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -4149,6 +4178,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = true
       ip_configuration {
         name = "primary"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
@@ -4158,6 +4188,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
       primary = false
       ip_configuration {
         name = "secondary"
+        primary = true
         subnet_id = "${azurerm_subnet.test.id}"
       }
   }
diff --git a/website/docs/r/virtual_machine_scale_set.html.markdown b/website/docs/r/virtual_machine_scale_set.html.markdown
index 02c189f56d2e..cda01debc21a 100644
--- a/website/docs/r/virtual_machine_scale_set.html.markdown
+++ b/website/docs/r/virtual_machine_scale_set.html.markdown
@@ -130,6 +130,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name                                   = "TestIPConfiguration"
+      primary                                = true
       subnet_id                              = "${azurerm_subnet.test.id}"
       load_balancer_backend_address_pool_ids = ["${azurerm_lb_backend_address_pool.bpepool.id}"]
       load_balancer_inbound_nat_rules_ids    = ["${element(azurerm_lb_nat_pool.lbnatpool.*.id, count.index)}"]
@@ -216,6 +217,7 @@ resource "azurerm_virtual_machine_scale_set" "test" {
 
     ip_configuration {
       name      = "TestIPConfiguration"
+      primary   = true
       subnet_id = "${azurerm_subnet.test.id}"
     }
   }
@@ -374,7 +376,7 @@ output "principal_id" {
 * `application_gateway_backend_address_pool_ids` - (Optional) Specifies an array of references to backend address pools of application gateways. A scale set can reference backend address pools of one application gateway. Multiple scale sets cannot use the same application gateway.
 * `load_balancer_backend_address_pool_ids` - (Optional) Specifies an array of references to backend address pools of load balancers. A scale set can reference backend address pools of one public and one internal load balancer. Multiple scale sets cannot use the same load balancer.
 * `load_balancer_inbound_nat_rules_ids` - (Optional) Specifies an array of references to inbound NAT rules for load balancers.
-* `primary` - (Optional) Specifies if this ip_configuration is the primary one.
+* `primary` - (Required) Specifies if this ip_configuration is the primary one.
 * `public_ip_address_configuration` - (Optional) describes a virtual machines scale set IP Configuration's
  PublicIPAddress configuration. The public_ip_address_configuration is documented below.