diff --git a/pkg/acsengine/defaults.go b/pkg/acsengine/defaults.go
index 7bcca7e153..74aab21bc3 100644
--- a/pkg/acsengine/defaults.go
+++ b/pkg/acsengine/defaults.go
@@ -371,7 +371,7 @@ func setPropertiesDefaults(cs *api.ContainerService, isUpgrade bool) (bool, erro
 
 	setHostedMasterNetworkDefaults(properties)
 
-	setAgentNetworkDefaults(properties)
+	setAgentNetworkDefaults(properties, isUpgrade)
 
 	setStorageDefaults(properties)
 	setExtensionDefaults(properties)
@@ -792,7 +792,7 @@ func setMasterNetworkDefaults(a *api.Properties, isUpgrade bool) {
 }
 
 // SetAgentNetworkDefaults for agents
-func setAgentNetworkDefaults(a *api.Properties) {
+func setAgentNetworkDefaults(a *api.Properties, isUpgrade bool) {
 	// configure the subnets if not in custom VNET
 	if a.MasterProfile != nil && !a.MasterProfile.IsCustomVNET() {
 		subnetCounter := 0
@@ -819,7 +819,7 @@ func setAgentNetworkDefaults(a *api.Properties) {
 		// On instances that support hyperthreading, Accelerated Networking is supported on VM instances with 4 or more vCPUs.
 		// Supported series are: D/DSv3, E/ESv3, Fsv2, and Ms/Mms.
 		if profile.AcceleratedNetworkingEnabled == nil {
-			profile.AcceleratedNetworkingEnabled = helpers.PointerToBool(helpers.AcceleratedNetworkingSupported(profile.VMSize))
+			profile.AcceleratedNetworkingEnabled = helpers.PointerToBool(!isUpgrade && helpers.AcceleratedNetworkingSupported(profile.VMSize))
 		}
 
 		// don't default Distro for OpenShift
diff --git a/pkg/acsengine/defaults_test.go b/pkg/acsengine/defaults_test.go
index 250c042f0a..81e1f4536b 100644
--- a/pkg/acsengine/defaults_test.go
+++ b/pkg/acsengine/defaults_test.go
@@ -548,7 +548,7 @@ func TestSetComponentsNetworkDefaults(t *testing.T) {
 		mockAPI := getMockAPIProperties("1.0.0")
 		mockAPI.OrchestratorProfile = &test.orchestratorProfile
 		setMasterNetworkDefaults(&mockAPI, false)
-		setAgentNetworkDefaults(&mockAPI)
+		setAgentNetworkDefaults(&mockAPI, false)
 		if mockAPI.MasterProfile.Distro != test.expectedDistro {
 			t.Fatalf("setMasterNetworkDefaults() test case %v did not return right Distro configurations %v != %v", test.name, mockAPI.MasterProfile.Distro, test.expectedDistro)
 		}