diff --git a/core/java/android/os/FileUtils.java b/core/java/android/os/FileUtils.java
index 44ae6eee21d63..760df45d2b698 100644
--- a/core/java/android/os/FileUtils.java
+++ b/core/java/android/os/FileUtils.java
@@ -316,6 +316,16 @@ public class FileUtils {
         stringToFile(file.getAbsolutePath(), string);
     }
 
+    /*
+     * Writes the bytes given in {@code content} to the file whose absolute path
+     * is {@code filename}.
+     */
+    public static void bytesToFile(String filename, byte[] content) throws IOException {
+        try (FileOutputStream fos = new FileOutputStream(filename)) {
+            fos.write(content);
+        }
+    }
+
     /**
      * Writes string to file. Basically same as "echo -n $string > $filename"
      *
diff --git a/services/core/java/com/android/server/pm/Settings.java b/services/core/java/com/android/server/pm/Settings.java
index eef8ce22ab48b..e3305850433b7 100644
--- a/services/core/java/com/android/server/pm/Settings.java
+++ b/services/core/java/com/android/server/pm/Settings.java
@@ -2470,7 +2470,10 @@ final class Settings {
 
         final File file = new File(dir, "appid");
         try {
-            FileUtils.stringToFile(file, Integer.toString(ps.appId));
+            // Note that the use of US_ASCII here is safe, we're only writing a decimal
+            // number to the file.
+            FileUtils.bytesToFile(file.getAbsolutePath(),
+                    Integer.toString(ps.appId).getBytes(StandardCharsets.US_ASCII));
             mKernelMapping.put(ps.name, ps.appId);
         } catch (IOException ignored) {
         }