diff --git a/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountCredentialsTest.java b/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountCredentialsTest.java
index ed26a0af3c6f..1bae2651f5ab 100644
--- a/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountCredentialsTest.java
+++ b/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountCredentialsTest.java
@@ -1777,6 +1777,8 @@ private void verifyJwtAccess(Map<String, List<String>> metadata, String expected
     assertNotNull(assertion, "Bearer assertion not found");
     JsonWebSignature signature =
         JsonWebSignature.parse(GsonFactory.getDefaultInstance(), assertion);
+    assertEquals("RS256", signature.getHeader().getAlgorithm());
+    assertEquals("JWT", signature.getHeader().getType());
     assertEquals(CLIENT_EMAIL, signature.getPayload().getIssuer());
     assertEquals(CLIENT_EMAIL, signature.getPayload().getSubject());
     if (expectedScopeClaim != null) {
@@ -1787,6 +1789,14 @@ private void verifyJwtAccess(Map<String, List<String>> metadata, String expected
       assertFalse(signature.getPayload().containsKey("scope"));
     }
     assertEquals(PRIVATE_KEY_ID, signature.getHeader().getKeyId());
+
+    Long iat = signature.getPayload().getIssuedAtTimeSeconds();
+    Long exp = signature.getPayload().getExpirationTimeSeconds();
+    assertNotNull(iat);
+    assertNotNull(exp);
+    assertEquals(3600L, exp - iat);
+    long currentTimeSecs = System.currentTimeMillis() / 1000;
+    assertTrue(Math.abs(currentTimeSecs - iat) < 60);
   }
 
   static GenericJson writeServiceAccountJson(
diff --git a/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountJwtAccessCredentialsTest.java b/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountJwtAccessCredentialsTest.java
index d961f7b1b685..8ef8bf895c16 100644
--- a/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountJwtAccessCredentialsTest.java
+++ b/google-auth-library-java/oauth2_http/javatests/com/google/auth/oauth2/ServiceAccountJwtAccessCredentialsTest.java
@@ -914,6 +914,8 @@ private void verifyJwtAccess(Map<String, List<String>> metadata, URI expectedAud
     }
     assertNotNull(assertion, "Bearer assertion not found");
     JsonWebSignature signature = JsonWebSignature.parse(JSON_FACTORY, assertion);
+    assertEquals("RS256", signature.getHeader().getAlgorithm());
+    assertEquals("JWT", signature.getHeader().getType());
     assertEquals(
         ServiceAccountJwtAccessCredentialsTest.SA_CLIENT_EMAIL, signature.getPayload().getIssuer());
     assertEquals(
@@ -922,6 +924,14 @@ private void verifyJwtAccess(Map<String, List<String>> metadata, URI expectedAud
     assertEquals(expectedAudience.toString(), signature.getPayload().getAudience());
     assertEquals(
         ServiceAccountJwtAccessCredentialsTest.SA_PRIVATE_KEY_ID, signature.getHeader().getKeyId());
+    
+    Long iat = signature.getPayload().getIssuedAtTimeSeconds();
+    Long exp = signature.getPayload().getExpirationTimeSeconds();
+    assertNotNull(iat);
+    assertNotNull(exp);
+    assertEquals(3600L, exp - iat);
+    long currentTimeSecs = System.currentTimeMillis() / 1000;
+    assertTrue(Math.abs(currentTimeSecs - iat) < 60);
   }
 
   private static void testFromStreamException(InputStream stream, String expectedMessageContent) {