diff --git a/lang/java/avro/src/main/java/org/apache/avro/SchemaCompatibility.java b/lang/java/avro/src/main/java/org/apache/avro/SchemaCompatibility.java
index 3e5628d9b3b..8b6a2839ad6 100644
--- a/lang/java/avro/src/main/java/org/apache/avro/SchemaCompatibility.java
+++ b/lang/java/avro/src/main/java/org/apache/avro/SchemaCompatibility.java
@@ -324,8 +324,10 @@ private SchemaCompatibilityResult calculateCompatibility(final Schema reader, fi
 
         // Reader compatible with all branches of a writer union is compatible
         if (writer.getType() == Schema.Type.UNION) {
+          int index = 0;
           for (Schema s : writer.getTypes()) {
-            result = result.mergedWith(getCompatibility(reader, s));
+            result = result.mergedWith(getCompatibility(Integer.toString(index), reader, s, location));
+            index++;
           }
           return result;
         }
diff --git a/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibility.java b/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibility.java
index f5e24597232..275bcfafede 100644
--- a/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibility.java
+++ b/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibility.java
@@ -233,6 +233,22 @@ void unionReaderWriterSubsetIncompatibility() {
     final Schema unionReader = Schema.createUnion(list(INT_SCHEMA, STRING_SCHEMA));
     final SchemaPairCompatibility result = checkReaderWriterCompatibility(unionReader, unionWriter);
     assertEquals(SchemaCompatibilityType.INCOMPATIBLE, result.getType());
+    assertEquals("/2", result.getResult().getIncompatibilities().get(0).getLocation());
+  }
+
+  @Test
+  void unionWriterSimpleReaderIncompatibility() {
+    Schema mandatorySchema = SchemaBuilder.record("Account").fields().name("age").type().intType().noDefault()
+        .endRecord();
+    Schema optionalSchema = SchemaBuilder.record("Account").fields().optionalInt("age").endRecord();
+
+    SchemaPairCompatibility compatibility = checkReaderWriterCompatibility(mandatorySchema, optionalSchema);
+
+    assertEquals(SchemaCompatibilityType.INCOMPATIBLE, compatibility.getType());
+
+    Incompatibility incompatibility = compatibility.getResult().getIncompatibilities().get(0);
+    assertEquals("reader type: INT not compatible with writer type: NULL", incompatibility.getMessage());
+    assertEquals("/fields/0/type/0", incompatibility.getLocation());
   }
 
   // -----------------------------------------------------------------------------------------------
diff --git a/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibilityTypeMismatch.java b/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibilityTypeMismatch.java
index ba625448da3..247e40404ba 100644
--- a/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibilityTypeMismatch.java
+++ b/lang/java/avro/src/test/java/org/apache/avro/TestSchemaCompatibilityTypeMismatch.java
@@ -90,11 +90,11 @@ public static Stream<Arguments> data() {
         Arguments.of(ENUM2_AB_SCHEMA, INT_SCHEMA, "reader type: ENUM not compatible with writer type: INT", "/"),
 
         Arguments.of(FLOAT_SCHEMA, INT_LONG_FLOAT_DOUBLE_UNION_SCHEMA,
-            "reader type: FLOAT not compatible with writer type: DOUBLE", "/"),
+            "reader type: FLOAT not compatible with writer type: DOUBLE", "/3"),
         Arguments.of(LONG_SCHEMA, INT_FLOAT_UNION_SCHEMA, "reader type: LONG not compatible with writer type: FLOAT",
-            "/"),
+            "/1"),
         Arguments.of(INT_SCHEMA, INT_FLOAT_UNION_SCHEMA, "reader type: INT not compatible with writer type: FLOAT",
-            "/"),
+            "/1"),
 
         Arguments.of(INT_LIST_RECORD, LONG_LIST_RECORD, "reader type: INT not compatible with writer type: LONG",
             "/fields/0/type"),