diff --git a/IntelUndiPkg/GigUndiDxe/AdapterInformation.c b/IntelUndiPkg/GigUndiDxe/AdapterInformation.c
index 8918c538e447..1cece79911b1 100644
--- a/IntelUndiPkg/GigUndiDxe/AdapterInformation.c
+++ b/IntelUndiPkg/GigUndiDxe/AdapterInformation.c
@@ -123,6 +123,7 @@ GetIpv6SupportInformationBlock (
 **/
 STATIC
 EFI_STATUS
+EFIAPI
 GetInformation (
   IN  EFI_ADAPTER_INFORMATION_PROTOCOL *This,
   IN  EFI_GUID *                        InformationType,
@@ -188,6 +189,7 @@ GetInformation (
 **/
 STATIC
 EFI_STATUS
+EFIAPI
 SetInformation (
   IN  EFI_ADAPTER_INFORMATION_PROTOCOL *This,
   IN  EFI_GUID *                        InformationType,
@@ -234,6 +236,7 @@ SetInformation (
 **/
 STATIC
 EFI_STATUS
+EFIAPI
 GetSupportedTypes (
   IN  EFI_ADAPTER_INFORMATION_PROTOCOL *This,
   OUT EFI_GUID **                       InfoTypesBuffer,
diff --git a/IntelUndiPkg/GigUndiDxe/ComponentName.c b/IntelUndiPkg/GigUndiDxe/ComponentName.c
index 70baf00f4a5d..2bf9bbfbe0e4 100644
--- a/IntelUndiPkg/GigUndiDxe/ComponentName.c
+++ b/IntelUndiPkg/GigUndiDxe/ComponentName.c
@@ -112,6 +112,7 @@ ComponentNameInitializeControllerName (
                                     language specified by Language.
 **/
 EFI_STATUS
+EFIAPI
 ComponentNameGetDriverName (
   IN  EFI_COMPONENT_NAME_PROTOCOL *This,
   IN  CHAR8 *                      Language,
@@ -182,6 +183,7 @@ ComponentNameGetDriverName (
                                     language specified by Language.
 **/
 EFI_STATUS
+EFIAPI
 ComponentNameGetControllerName (
   IN  EFI_COMPONENT_NAME_PROTOCOL *                               This,
   IN  EFI_HANDLE                                                  ControllerHandle,
diff --git a/IntelUndiPkg/GigUndiDxe/ComponentName.h b/IntelUndiPkg/GigUndiDxe/ComponentName.h
index 5a3d414c6970..0b93a5410fc0 100644
--- a/IntelUndiPkg/GigUndiDxe/ComponentName.h
+++ b/IntelUndiPkg/GigUndiDxe/ComponentName.h
@@ -65,6 +65,7 @@ ComponentNameInitializeControllerName (
                                     language specified by Language.
 **/
 EFI_STATUS
+EFIAPI
 ComponentNameGetDriverName (
   IN  EFI_COMPONENT_NAME_PROTOCOL *This,
   IN  CHAR8 *                      Language,
diff --git a/IntelUndiPkg/GigUndiDxe/DriverConfiguration.c b/IntelUndiPkg/GigUndiDxe/DriverConfiguration.c
index 20d40ab672ef..99e086d81044 100644
--- a/IntelUndiPkg/GigUndiDxe/DriverConfiguration.c
+++ b/IntelUndiPkg/GigUndiDxe/DriverConfiguration.c
@@ -310,6 +310,7 @@ GigUndiDriverConfigurationDisplayMenu (
    @retval   EFI_SUCCESS       Configuration was successful
 **/
 EFI_STATUS
+EFIAPI
 GigUndiDriverConfigurationSetOptions (
   IN EFI_DRIVER_CONFIGURATION_PROTOCOL *          This,
   IN EFI_HANDLE                                   ControllerHandle,
@@ -418,6 +419,7 @@ GigUndiDriverConfigurationSetOptions (
    @retval   EFI_SUCCESS   Always returned
 **/
 EFI_STATUS
+EFIAPI
 GigUndiDriverConfigurationOptionsValid (
   IN EFI_DRIVER_CONFIGURATION_PROTOCOL *   This,
   IN EFI_HANDLE                            ControllerHandle,
@@ -442,6 +444,7 @@ GigUndiDriverConfigurationOptionsValid (
    @retval   EFI_SUCCESS       Configuration was successful
 **/
 EFI_STATUS
+EFIAPI
 GigUndiDriverConfigurationForceDefaults (
   IN EFI_DRIVER_CONFIGURATION_PROTOCOL *                   This,
   IN EFI_HANDLE                                            ControllerHandle,
diff --git a/IntelUndiPkg/GigUndiDxe/DriverDiagnostics.c b/IntelUndiPkg/GigUndiDxe/DriverDiagnostics.c
index aceb015e480f..f6152cd24c59 100644
--- a/IntelUndiPkg/GigUndiDxe/DriverDiagnostics.c
+++ b/IntelUndiPkg/GigUndiDxe/DriverDiagnostics.c
@@ -1394,6 +1394,7 @@ Error:
                                     ChildHandle did not pass the diagnostic.
 **/
 EFI_STATUS
+EFIAPI
 GigUndiDriverDiagnosticsRunDiagnostics (
   IN EFI_DRIVER_DIAGNOSTICS_PROTOCOL *           This,
   IN EFI_HANDLE                                  ControllerHandle,
diff --git a/IntelUndiPkg/GigUndiDxe/DriverHealth.c b/IntelUndiPkg/GigUndiDxe/DriverHealth.c
index b5b7db5fd814..ea306843679a 100644
--- a/IntelUndiPkg/GigUndiDxe/DriverHealth.c
+++ b/IntelUndiPkg/GigUndiDxe/DriverHealth.c
@@ -44,6 +44,7 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
    @retval      !EFI_SUCCESS      Failure to retrieve health status
 **/
 EFI_STATUS
+EFIAPI
 GetHealthStatus (
   IN  EFI_DRIVER_HEALTH_PROTOCOL *     This,
   IN  EFI_HANDLE                       ControllerHandle, OPTIONAL
@@ -119,6 +120,7 @@ GetHealthStatus (
    @retval   EFI_UNSUPPORTED   This function is unsupported
 **/
 EFI_STATUS
+EFIAPI
 Repair (
   IN  EFI_DRIVER_HEALTH_PROTOCOL                *This,
   IN  EFI_HANDLE                                ControllerHandle,
diff --git a/IntelUndiPkg/GigUndiDxe/StartStop.c b/IntelUndiPkg/GigUndiDxe/StartStop.c
index 32bed7ce288d..a788da247e6d 100644
--- a/IntelUndiPkg/GigUndiDxe/StartStop.c
+++ b/IntelUndiPkg/GigUndiDxe/StartStop.c
@@ -38,6 +38,7 @@ EFI_GUID gEfiStartStopProtocolGuid = EFI_DRIVER_STOP_PROTOCOL_GUID;
    @retval   EFI_SUCCESS   Driver is stopped successfully
 **/
 EFI_STATUS
+EFIAPI
 StopDriver (
   IN EFI_DRIVER_STOP_PROTOCOL *This
   )
@@ -62,6 +63,7 @@ StopDriver (
    @retval   EFI_SUCCESS   If driver has restarted successfully
 **/
 EFI_STATUS
+EFIAPI
 StartDriver (
   IN EFI_DRIVER_STOP_PROTOCOL *This
   )
