diff --git a/src/main/java/com/bugsnag/android/Client.java b/src/main/java/com/bugsnag/android/Client.java
index 3330c0d1c0..74166f2ab2 100644
--- a/src/main/java/com/bugsnag/android/Client.java
+++ b/src/main/java/com/bugsnag/android/Client.java
@@ -6,6 +6,7 @@
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
 import android.text.TextUtils;
+import java.util.Locale;
 
 /**
  * A Bugsnag Client instance allows you to use Bugsnag in your Android app.
@@ -617,7 +618,7 @@ public void run() {
     void deliver(Notification notification, Error error) {
         try {
             int errorCount = notification.deliver();
-            Logger.info(String.format("Sent %d new error(s) to Bugsnag", errorCount));
+            Logger.info(String.format(Locale.US, "Sent %d new error(s) to Bugsnag", errorCount));
         } catch (HttpClient.NetworkException e) {
             Logger.info("Could not send error(s) to Bugsnag, saving to disk to send later");
 
diff --git a/src/main/java/com/bugsnag/android/DeviceData.java b/src/main/java/com/bugsnag/android/DeviceData.java
index bb0d3988e6..051b3eecf7 100644
--- a/src/main/java/com/bugsnag/android/DeviceData.java
+++ b/src/main/java/com/bugsnag/android/DeviceData.java
@@ -101,7 +101,7 @@ private static String getScreenResolution(Context appContext) {
         if (resources == null)
             return null;
         DisplayMetrics metrics = resources.getDisplayMetrics();
-        return String.format("%dx%d", Math.max(metrics.widthPixels, metrics.heightPixels), Math.min(metrics.widthPixels, metrics.heightPixels));
+        return String.format(Locale.US, "%dx%d", Math.max(metrics.widthPixels, metrics.heightPixels), Math.min(metrics.widthPixels, metrics.heightPixels));
     }
 
     /**
diff --git a/src/main/java/com/bugsnag/android/ErrorStore.java b/src/main/java/com/bugsnag/android/ErrorStore.java
index e74fa901d4..7d3d18f417 100644
--- a/src/main/java/com/bugsnag/android/ErrorStore.java
+++ b/src/main/java/com/bugsnag/android/ErrorStore.java
@@ -5,6 +5,7 @@
 import java.io.Writer;
 import java.util.Arrays;
 import java.util.List;
+import java.util.Locale;
 
 import android.content.Context;
 
@@ -52,7 +53,7 @@ public void run() {
 
                 File[] errorFiles = exceptionDir.listFiles();
                 if(errorFiles != null && errorFiles.length > 0) {
-                    Logger.info(String.format("Sending %d saved error(s) to Bugsnag", errorFiles.length));
+                    Logger.info(String.format(Locale.US, "Sending %d saved error(s) to Bugsnag", errorFiles.length));
 
                     for(File errorFile : errorFiles) {
                         try {
@@ -94,7 +95,7 @@ void write(Error error) {
             }
         }
 
-        String filename = String.format("%s%d.json", path, System.currentTimeMillis());
+        String filename = String.format(Locale.US, "%s%d.json", path, System.currentTimeMillis());
         Writer out = null;
         try {
             out = new FileWriter(filename);
diff --git a/src/main/java/com/bugsnag/android/HttpClient.java b/src/main/java/com/bugsnag/android/HttpClient.java
index c9b5d1f212..80faac15c1 100644
--- a/src/main/java/com/bugsnag/android/HttpClient.java
+++ b/src/main/java/com/bugsnag/android/HttpClient.java
@@ -7,10 +7,12 @@
 import java.net.HttpURLConnection;
 import java.net.URL;
 
+import java.util.Locale;
+
 class HttpClient {
     static class BadResponseException extends Exception {
         public BadResponseException(String url, int responseCode) {
-            super(String.format("Got non-200 response code (%d) from %s", responseCode, url));
+            super(String.format(Locale.US, "Got non-200 response code (%d) from %s", responseCode, url));
         }
     }