diff --git a/core/src/test/java/com/google/common/truth/IterableSubjectTest.java b/core/src/test/java/com/google/common/truth/IterableSubjectTest.java
index 71254721c..8f012a2f1 100644
--- a/core/src/test/java/com/google/common/truth/IterableSubjectTest.java
+++ b/core/src/test/java/com/google/common/truth/IterableSubjectTest.java
@@ -23,6 +23,7 @@
 import static com.google.common.truth.Truth.assertThat;
 import static java.lang.String.CASE_INSENSITIVE_ORDER;
 import static java.util.Arrays.asList;
+import static java.util.Collections.singleton;
 import static org.junit.Assert.assertThrows;
 
 import com.google.common.collect.ImmutableList;
@@ -814,10 +815,12 @@ public void containsExactlyWithDuplicatesOutOfOrder() {
   }
 
   @Test
+  // We intentionally test the behavior of the method under a call that will soon fail.
+  @SuppressWarnings("NullNeedsCastForVarargs")
   @J2ktIncompatible // Kotlin can't pass a null array for a varargs parameter
   public void containsExactlyWithOnlyNullPassedAsNullArray() {
-    // Truth is tolerant of this erroneous varargs call.
-    Iterable<Object> actual = asList((Object) null);
+    Iterable<Object> actual = singleton(null);
+    // We are changing Truth from tolerating this erroneous varargs call to not tolerating it.
     try {
       assertThat(actual).containsExactly((Object[]) null);
     } catch (NullPointerException e) {
diff --git a/core/src/test/java/com/google/common/truth/StreamSubjectTest.java b/core/src/test/java/com/google/common/truth/StreamSubjectTest.java
index 9ce30bcce..d2b1c260d 100644
--- a/core/src/test/java/com/google/common/truth/StreamSubjectTest.java
+++ b/core/src/test/java/com/google/common/truth/StreamSubjectTest.java
@@ -21,6 +21,7 @@
 import static com.google.common.truth.FailureAssertions.assertFailureValue;
 import static com.google.common.truth.Truth.assertThat;
 import static java.util.Arrays.asList;
+import static java.util.Collections.singleton;
 
 import java.util.stream.Stream;
 import org.junit.Test;
@@ -316,8 +317,11 @@ public void containsExactly_nullObject() {
 
   @Test
   @J2ktIncompatible // Kotlin can't pass a null array for a varargs parameter
+  // We intentionally test the behavior of the method under a call that will soon fail.
+  @SuppressWarnings("NullNeedsCastForVarargs")
   public void containsExactly_nullObjectArray() {
-    StreamSubject subject = assertThat(Stream.of((Object) null));
+    StreamSubject subject = assertThat(singleton(null).stream());
+    // We are changing Truth from tolerating this erroneous varargs call to not tolerating it.
     try {
       subject.containsExactly((Object[]) null);
     } catch (NullPointerException e) {