diff --git a/api/system-current.txt b/api/system-current.txt
index e2b6960f54212..a2f83fd7783ff 100644
--- a/api/system-current.txt
+++ b/api/system-current.txt
@@ -3275,7 +3275,7 @@ package android.net {
     method @Nullable public String getDomains();
     method @Nullable public java.net.InetAddress getGateway();
     method @Nullable public android.net.LinkAddress getIpAddress();
-    method @NonNull public java.util.List<android.net.RouteInfo> getRoutes(String);
+    method @NonNull public java.util.List<android.net.RouteInfo> getRoutes(@Nullable String);
     method public void setDomains(@Nullable String);
     method public void setGateway(@Nullable java.net.InetAddress);
     method public void setIpAddress(@Nullable android.net.LinkAddress);
@@ -3495,7 +3495,7 @@ package android.net.metrics {
   }
 
   public final class ValidationProbeEvent implements android.net.metrics.IpConnectivityLog.Event {
-    method public static String getProbeName(int);
+    method @NonNull public static String getProbeName(int);
     field public static final int DNS_FAILURE = 0; // 0x0
     field public static final int DNS_SUCCESS = 1; // 0x1
     field public static final int PROBE_DNS = 0; // 0x0
diff --git a/api/test-current.txt b/api/test-current.txt
index 43bbca30946d0..bb1a957da589d 100644
--- a/api/test-current.txt
+++ b/api/test-current.txt
@@ -695,7 +695,7 @@ package android.net {
     method @Nullable public String getDomains();
     method @Nullable public java.net.InetAddress getGateway();
     method @Nullable public android.net.LinkAddress getIpAddress();
-    method @NonNull public java.util.List<android.net.RouteInfo> getRoutes(String);
+    method @NonNull public java.util.List<android.net.RouteInfo> getRoutes(@Nullable String);
     method public void setDomains(@Nullable String);
     method public void setGateway(@Nullable java.net.InetAddress);
     method public void setIpAddress(@Nullable android.net.LinkAddress);
@@ -914,7 +914,7 @@ package android.net.metrics {
   }
 
   public final class ValidationProbeEvent implements android.net.metrics.IpConnectivityLog.Event {
-    method public static String getProbeName(int);
+    method @NonNull public static String getProbeName(int);
     field public static final int DNS_FAILURE = 0; // 0x0
     field public static final int DNS_SUCCESS = 1; // 0x1
     field public static final int PROBE_DNS = 0; // 0x0
diff --git a/core/java/android/net/StaticIpConfiguration.java b/core/java/android/net/StaticIpConfiguration.java
index 0728d83cbdb1e..14dbca0183f0a 100644
--- a/core/java/android/net/StaticIpConfiguration.java
+++ b/core/java/android/net/StaticIpConfiguration.java
@@ -134,7 +134,7 @@ public final class StaticIpConfiguration implements Parcelable {
      * route to the gateway as well. This configuration is arguably invalid, but it used to work
      * in K and earlier, and other OSes appear to accept it.
      */
-    public @NonNull List<RouteInfo> getRoutes(String iface) {
+    public @NonNull List<RouteInfo> getRoutes(@Nullable String iface) {
         List<RouteInfo> routes = new ArrayList<RouteInfo>(3);
         if (ipAddress != null) {
             RouteInfo connectedRoute = new RouteInfo(ipAddress, null, iface);
diff --git a/core/java/android/net/metrics/ValidationProbeEvent.java b/core/java/android/net/metrics/ValidationProbeEvent.java
index 9eb87ef43cbb7..ebca7e6d56078 100644
--- a/core/java/android/net/metrics/ValidationProbeEvent.java
+++ b/core/java/android/net/metrics/ValidationProbeEvent.java
@@ -153,11 +153,14 @@ public final class ValidationProbeEvent implements IpConnectivityLog.Event {
         return (probeType & 0xff) | (firstValidation ? FIRST_VALIDATION : REVALIDATION);
     }
 
-    public static String getProbeName(int probeType) {
+    /**
+     * Get the name of a probe specified by its probe type.
+     */
+    public static @NonNull String getProbeName(int probeType) {
         return Decoder.constants.get(probeType & 0xff, "PROBE_???");
     }
 
-    private static String getValidationStage(int probeType) {
+    private static @NonNull String getValidationStage(int probeType) {
         return Decoder.constants.get(probeType & 0xff00, "UNKNOWN");
     }