diff --git a/lang/java/avro/src/main/java/org/apache/avro/io/parsing/Symbol.java b/lang/java/avro/src/main/java/org/apache/avro/io/parsing/Symbol.java
index a18f3fdbcd5..7009de99735 100644
--- a/lang/java/avro/src/main/java/org/apache/avro/io/parsing/Symbol.java
+++ b/lang/java/avro/src/main/java/org/apache/avro/io/parsing/Symbol.java
@@ -475,6 +475,16 @@ public int findLabel(String label) {
             return i;
           }
         }
+        // AVRO-4135 We are a bit more flexible here since we have to deal with the C
+        // serializer being less strict, so
+        // we fall back to looking up unqualified names.
+        for (int i = 0; i < labels.length; i++) {
+          String candidate = labels[i];
+          if (candidate != null && candidate.length() > label.length()
+              && candidate.charAt(candidate.length() - label.length() - 1) == '.' && candidate.endsWith(label)) {
+            return i;
+          }
+        }
       }
       return -1;
     }
diff --git a/lang/java/avro/src/test/java/org/apache/avro/io/TestJsonDecoder.java b/lang/java/avro/src/test/java/org/apache/avro/io/TestJsonDecoder.java
index 05057139600..39600af5d4d 100644
--- a/lang/java/avro/src/test/java/org/apache/avro/io/TestJsonDecoder.java
+++ b/lang/java/avro/src/test/java/org/apache/avro/io/TestJsonDecoder.java
@@ -92,4 +92,16 @@ void testIntWithError() throws IOException {
     JsonDecoder decoder = DecoderFactory.get().jsonDecoder(schema, record);
     Assertions.assertThrows(AvroTypeException.class, () -> reader.read(null, decoder));
   }
+
+  @Test
+  void testUnionTypeQualification() throws Exception {
+    final Schema schema = SchemaBuilder.unionOf().nullType().and()
+        .type(SchemaBuilder.record("r").namespace("space").fields().endRecord()).endUnion();
+    GenericDatumReader<GenericRecord> reader = new GenericDatumReader<>(schema, schema);
+    JsonDecoder decoder = DecoderFactory.get().jsonDecoder(schema, "{\"space.r\": {}}");
+    assertEquals("space.r", reader.read(null, decoder).getSchema().getFullName());
+    // AVRO-4135: C json encoder uses unqualified types.
+    decoder = DecoderFactory.get().jsonDecoder(schema, "{\"r\": {}}");
+    assertEquals("space.r", reader.read(null, decoder).getSchema().getFullName());
+  }
 }