diff --git a/lang/java/avro/src/main/java/org/apache/avro/generic/GenericData.java b/lang/java/avro/src/main/java/org/apache/avro/generic/GenericData.java
index 0098d8da5e0..ebbac9a3228 100644
--- a/lang/java/avro/src/main/java/org/apache/avro/generic/GenericData.java
+++ b/lang/java/avro/src/main/java/org/apache/avro/generic/GenericData.java
@@ -185,6 +185,9 @@ public <T> Conversion<T> getConversionByClass(Class<T> datumClass) {
    */
   @SuppressWarnings("unchecked")
   public <T> Conversion<T> getConversionByClass(Class<T> datumClass, LogicalType logicalType) {
+    if (logicalType == null) {
+      return null;
+    }
     Map<String, Conversion<?>> conversions = conversionsByClass.get(datumClass);
     if (conversions != null) {
       return (Conversion<T>) conversions.get(logicalType.getName());
diff --git a/lang/java/avro/src/test/java/org/apache/avro/reflect/TestReflectData.java b/lang/java/avro/src/test/java/org/apache/avro/reflect/TestReflectData.java
index 40d9ad6decb..a8e6f8e41ab 100644
--- a/lang/java/avro/src/test/java/org/apache/avro/reflect/TestReflectData.java
+++ b/lang/java/avro/src/test/java/org/apache/avro/reflect/TestReflectData.java
@@ -39,9 +39,16 @@
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.lessThan;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNull;
 import static org.junit.jupiter.api.Assertions.assertThrows;
 
 public class TestReflectData {
+  @Test
+  void getConversionByClassWithNullLogicalTypeReturnsNull() {
+    // BigDecimal has a conversion registered by default but a null logicalType
+    assertNull(ReflectData.get().getConversionByClass(java.math.BigDecimal.class, null));
+  }
+
   @Test
   @SuppressWarnings("unchecked")
   void weakSchemaCaching() throws Exception {