diff --git a/src/main/java/org/apache/commons/csv/Assertions.java b/src/main/java/org/apache/commons/csv/Assertions.java
index f22002d8..057b3d74 100644
--- a/src/main/java/org/apache/commons/csv/Assertions.java
+++ b/src/main/java/org/apache/commons/csv/Assertions.java
@@ -30,7 +30,7 @@ final class Assertions {
         // can not be instantiated
     }
 
-    public static void notNull(final Object parameter, final String parameterName) {
+    static void notNull(final Object parameter, final String parameterName) {
         if (parameter == null) {
             throw new IllegalArgumentException("Parameter '" + parameterName + "' must not be null!");
         }