diff --git a/src/main/java/com/nexmo/client/auth/JWTAuthMethod.java b/src/main/java/com/nexmo/client/auth/JWTAuthMethod.java
index 94eea1037..bee919cfd 100644
--- a/src/main/java/com/nexmo/client/auth/JWTAuthMethod.java
+++ b/src/main/java/com/nexmo/client/auth/JWTAuthMethod.java
@@ -44,9 +44,12 @@
 import java.util.regex.Pattern;
 
 public class JWTAuthMethod extends AbstractAuthMethod {
-    private static final Pattern pemPattern = Pattern.compile("-----BEGIN PRIVATE KEY-----" +
-            "(.*\\n)" +
-            "-----END PRIVATE KEY-----\\n?", Pattern.MULTILINE | Pattern.DOTALL);
+    private static final Pattern pemPattern = Pattern.compile(
+            "-----BEGIN PRIVATE KEY-----" + // File header
+            "(.*\\n)" +                     // Key data
+            "-----END PRIVATE KEY-----" +   // File footer
+            "\\n?",                         // Optional trailing line break
+            Pattern.MULTILINE | Pattern.DOTALL);
     public final int SORT_KEY = 10;
     private String applicationId;
     private JWTSigner signer;