diff --git a/google-cloud-clients/google-cloud-datastore/src/main/java/com/google/cloud/datastore/Validator.java b/google-cloud-clients/google-cloud-datastore/src/main/java/com/google/cloud/datastore/Validator.java
index 11eb0b71380d..28a07001461f 100644
--- a/google-cloud-clients/google-cloud-datastore/src/main/java/com/google/cloud/datastore/Validator.java
+++ b/google-cloud-clients/google-cloud-datastore/src/main/java/com/google/cloud/datastore/Validator.java
@@ -40,7 +40,7 @@ private Validator() {
   static String validateDatabase(String projectId) {
     checkArgument(!Strings.isNullOrEmpty(projectId), "projectId can't be empty or null");
     checkArgument(PROJECT_ID_PATTERN.matcher(projectId).matches(),
-        "projectId must match the following pattern: " + PROJECT_ID_PATTERN.pattern());
+    	"projectId " + projectId + " does not match the required pattern: " + PROJECT_ID_PATTERN.pattern());
     return projectId;
   }