diff --git a/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java b/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java
index d2f44d3..b6240c4 100644
--- a/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java
+++ b/Tethering/src/com/android/networkstack/tethering/TetheringConfiguration.java
@@ -170,8 +170,16 @@
 
         mUsbTetheringFunction = getUsbTetheringFunction(res);
 
-        tetherableUsbRegexs = getResourceStringArray(res, R.array.config_tether_usb_regexs);
-        tetherableNcmRegexs = getResourceStringArray(res, R.array.config_tether_ncm_regexs);
+        final String[] ncmRegexs = getResourceStringArray(res, R.array.config_tether_ncm_regexs);
+        // If usb tethering use NCM and config_tether_ncm_regexs is not empty, use
+        // config_tether_ncm_regexs for tetherableUsbRegexs.
+        if (isUsingNcm() && (ncmRegexs.length != 0)) {
+            tetherableUsbRegexs = ncmRegexs;
+            tetherableNcmRegexs = EMPTY_STRING_ARRAY;
+        } else {
+            tetherableUsbRegexs = getResourceStringArray(res, R.array.config_tether_usb_regexs);
+            tetherableNcmRegexs = ncmRegexs;
+        }
         // TODO: Evaluate deleting this altogether now that Wi-Fi always passes
         // us an interface name. Careful consideration needs to be given to
         // implications for Settings and for provisioning checks.
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java
index 0f940d8..c0c2ab9 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringConfigurationTest.java
@@ -30,6 +30,7 @@
 import static com.android.networkstack.tethering.TetheringConfiguration.TETHER_USB_NCM_FUNCTION;
 import static com.android.networkstack.tethering.TetheringConfiguration.TETHER_USB_RNDIS_FUNCTION;
 
+import static org.junit.Assert.assertArrayEquals;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertTrue;
@@ -600,4 +601,48 @@
     private void setTetherForceUsbFunctions(final int value) {
         setTetherForceUsbFunctions(Integer.toString(value));
     }
+
+    @Test
+    public void testNcmRegexs() throws Exception {
+        final String[] rndisRegexs = {"test_rndis\\d"};
+        final String[] ncmRegexs   = {"test_ncm\\d"};
+        final String[] rndisNcmRegexs   = {"test_rndis\\d", "test_ncm\\d"};
+
+        // cfg.isUsingNcm = false.
+        when(mResources.getInteger(R.integer.config_tether_usb_functions)).thenReturn(
+                TETHER_USB_RNDIS_FUNCTION);
+        setUsbAndNcmRegexs(rndisRegexs, ncmRegexs);
+        assertUsbAndNcmRegexs(rndisRegexs, ncmRegexs);
+
+        setUsbAndNcmRegexs(rndisNcmRegexs, new String[0]);
+        assertUsbAndNcmRegexs(rndisNcmRegexs, new String[0]);
+
+        // cfg.isUsingNcm = true.
+        when(mResources.getInteger(R.integer.config_tether_usb_functions)).thenReturn(
+                TETHER_USB_NCM_FUNCTION);
+        setUsbAndNcmRegexs(rndisRegexs, ncmRegexs);
+        assertUsbAndNcmRegexs(ncmRegexs, new String[0]);
+
+        setUsbAndNcmRegexs(rndisNcmRegexs, new String[0]);
+        assertUsbAndNcmRegexs(rndisNcmRegexs, new String[0]);
+
+        // Check USB regex is not overwritten by the NCM regex after force to use rndis from
+        // Settings.
+        setUsbAndNcmRegexs(rndisRegexs, ncmRegexs);
+        setTetherForceUsbFunctions(TETHER_USB_RNDIS_FUNCTION);
+        assertUsbAndNcmRegexs(rndisRegexs, ncmRegexs);
+    }
+
+    private void setUsbAndNcmRegexs(final String[] usbRegexs, final String[] ncmRegexs) {
+        when(mResources.getStringArray(R.array.config_tether_usb_regexs)).thenReturn(usbRegexs);
+        when(mResources.getStringArray(R.array.config_tether_ncm_regexs)).thenReturn(ncmRegexs);
+    }
+
+    private void assertUsbAndNcmRegexs(final String[] usbRegexs, final String[] ncmRegexs) {
+        final TetheringConfiguration cfg =
+                new TetheringConfiguration(mMockContext, mLog, INVALID_SUBSCRIPTION_ID);
+        assertArrayEquals(usbRegexs, cfg.tetherableUsbRegexs);
+        assertArrayEquals(ncmRegexs, cfg.tetherableNcmRegexs);
+    }
+
 }
diff --git a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
index 5aebca0..f999dfa 100644
--- a/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
+++ b/Tethering/tests/unit/src/com/android/networkstack/tethering/TetheringTest.java
@@ -2665,12 +2665,6 @@
         forceUsbTetheringUse(TETHER_USB_NCM_FUNCTION);
         verifyUsbTetheringStopDueToSettingChange(TEST_NCM_IFNAME);
 
-        // TODO: move this into setup after allowing configure TEST_NCM_REGEX into
-        // config_tether_usb_regexs and config_tether_ncm_regexs at the same time.
-        when(mResources.getStringArray(R.array.config_tether_usb_regexs))
-                .thenReturn(new String[] {TEST_RNDIS_REGEX, TEST_NCM_REGEX});
-        sendConfigurationChanged();
-
         // If TETHERING_USB is forced to use ncm function, TETHERING_NCM would no longer be
         // available.
         final ResultListener ncmResult = new ResultListener(TETHER_ERROR_SERVICE_UNAVAIL);