diff --git a/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/OAuth2UtilsTest.java b/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/OAuth2UtilsTest.java
index f540ac41d2b9..92bec0231fb6 100644
--- a/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/OAuth2UtilsTest.java
+++ b/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/OAuth2UtilsTest.java
@@ -40,6 +40,20 @@
 /** Tests for {@link OAuth2Utils}. */
 class OAuth2UtilsTest {
 
+  @Test
+  void testPrivateKeyFromPkcs8_invalidKey() {
+    String invalidKey = "-----BEGIN PRIVATE KEY-----\n" +
+        "INVALID_KEY_DATA\n" +
+        "-----END PRIVATE KEY-----\n";
+    assertThrows(java.io.IOException.class, () -> OAuth2Utils.privateKeyFromPkcs8(invalidKey));
+  }
+
+  @Test
+  void testPrivateKeyFromPkcs8_malformedPem() {
+    String malformedKey = "just some random string";
+    assertThrows(java.io.IOException.class, () -> OAuth2Utils.privateKeyFromPkcs8(malformedKey));
+  }
+
   @Test
   void testValidCredentials() {
     String username = "testUser";