diff --git a/guava-testlib/src/com/google/common/testing/NullPointerTester.java b/guava-testlib/src/com/google/common/testing/NullPointerTester.java
index <HASH>..<HASH> 100644
--- a/guava-testlib/src/com/google/common/testing/NullPointerTester.java
+++ b/guava-testlib/src/com/google/common/testing/NullPointerTester.java
@@ -337,8 +337,8 @@ public final class NullPointerTester {
       @SuppressWarnings("unchecked") // We'll get a runtime exception if the type is wrong.
       Invokable<Object, ?> unsafe = (Invokable<Object, ?>) invokable;
       unsafe.invoke(instance, params);
-      Assert.fail("No exception thrown from " + invokable +
-          Arrays.toString(params) + " for " + testedClass);
+      Assert.fail("No exception thrown for parameter at index " + paramIndex
+          + " from " + invokable + Arrays.toString(params) + " for " + testedClass);
     } catch (InvocationTargetException e) {
       Throwable cause = e.getCause();
       if (policy.isExpectedType(cause)) {
Include failing parameter index in exception - useful for inherited classes where it's
non-obvious which parameter is failing null check.
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Created by MOE: <URL>