diff --git a/azurerm/resource_arm_application_gateway.go b/azurerm/resource_arm_application_gateway.go
index 49a343f045ed..d8d42ec06fbb 100644
--- a/azurerm/resource_arm_application_gateway.go
+++ b/azurerm/resource_arm_application_gateway.go
@@ -1172,17 +1172,19 @@ func expandApplicationGatewayBackendAddressPools(d *schema.ResourceData) *[]netw
 			})
 		}
 
-		// TODO: remove in 2.0
-		for _, ip := range v["ip_address_list"].([]interface{}) {
-			backendAddresses = append(backendAddresses, network.ApplicationGatewayBackendAddress{
-				IPAddress: utils.String(ip.(string)),
-			})
-		}
-		// TODO: remove in 2.0
-		for _, ip := range v["fqdn_list"].([]interface{}) {
-			backendAddresses = append(backendAddresses, network.ApplicationGatewayBackendAddress{
-				Fqdn: utils.String(ip.(string)),
-			})
+		if len(backendAddresses) == 0 {
+			// TODO: remove in 2.0
+			for _, ip := range v["ip_address_list"].([]interface{}) {
+				backendAddresses = append(backendAddresses, network.ApplicationGatewayBackendAddress{
+					IPAddress: utils.String(ip.(string)),
+				})
+			}
+			// TODO: remove in 2.0
+			for _, ip := range v["fqdn_list"].([]interface{}) {
+				backendAddresses = append(backendAddresses, network.ApplicationGatewayBackendAddress{
+					Fqdn: utils.String(ip.(string)),
+				})
+			}
 		}
 
 		name := v["name"].(string)