diff --git a/lucene/core/src/java/org/apache/lucene/search/SynonymQuery.java b/lucene/core/src/java/org/apache/lucene/search/SynonymQuery.java
index ca32a7d7bb8e..7e314870f9c7 100644
--- a/lucene/core/src/java/org/apache/lucene/search/SynonymQuery.java
+++ b/lucene/core/src/java/org/apache/lucene/search/SynonymQuery.java
@@ -113,7 +113,7 @@ public SynonymQuery build() {
    */
   private SynonymQuery(TermAndBoost[] terms, String field) {
     this.terms = Objects.requireNonNull(terms);
-    this.field = field;
+    this.field = Objects.requireNonNull(field);
   }
 
   public List<Term> getTerms() {
@@ -146,7 +146,9 @@ public int hashCode() {
 
   @Override
   public boolean equals(Object other) {
-    return sameClassAs(other) && Arrays.equals(terms, ((SynonymQuery) other).terms);
+    return sameClassAs(other)
+        && field.equals(((SynonymQuery) other).field)
+        && Arrays.equals(terms, ((SynonymQuery) other).terms);
   }
 
   @Override
diff --git a/lucene/core/src/test/org/apache/lucene/search/TestSynonymQuery.java b/lucene/core/src/test/org/apache/lucene/search/TestSynonymQuery.java
index 123307e75f8e..ae026a87367f 100644
--- a/lucene/core/src/test/org/apache/lucene/search/TestSynonymQuery.java
+++ b/lucene/core/src/test/org/apache/lucene/search/TestSynonymQuery.java
@@ -73,6 +73,18 @@ public void testEquals() {
             .addTerm(new Term("field", "c"), 0.2f)
             .addTerm(new Term("field", "d"))
             .build());
+
+    QueryUtils.checkUnequal(
+        new SynonymQuery.Builder("field").addTerm(new Term("field", "a"), 0.4f).build(),
+        new SynonymQuery.Builder("field").addTerm(new Term("field", "b"), 0.4f).build());
+
+    QueryUtils.checkUnequal(
+        new SynonymQuery.Builder("field").addTerm(new Term("field", "a"), 0.2f).build(),
+        new SynonymQuery.Builder("field").addTerm(new Term("field", "a"), 0.4f).build());
+
+    QueryUtils.checkUnequal(
+        new SynonymQuery.Builder("field1").addTerm(new Term("field1", "b"), 0.4f).build(),
+        new SynonymQuery.Builder("field2").addTerm(new Term("field2", "b"), 0.4f).build());
   }
 
   public void testBogusParams() {
@@ -127,6 +139,12 @@ public void testBogusParams() {
         () -> {
           new SynonymQuery.Builder("field1").addTerm(new Term("field1", "a"), -0f);
         });
+
+    expectThrows(
+        NullPointerException.class,
+        () -> new SynonymQuery.Builder(null).addTerm(new Term("field1", "a"), -0f));
+
+    expectThrows(NullPointerException.class, () -> new SynonymQuery.Builder(null).build());
   }
 
   public void testToString() {