diff --git a/src/com/sun/jna/NativeLibrary.java b/src/com/sun/jna/NativeLibrary.java
index 4a595db2a..a0d49ed18 100644
--- a/src/com/sun/jna/NativeLibrary.java
+++ b/src/com/sun/jna/NativeLibrary.java
@@ -95,7 +95,7 @@ public long getSymbolAddress(long handle, String name, SymbolProvider parent) {
         }
     };
 
-    private Cleaner.Cleanable cleanable;
+    private final Cleaner.Cleanable cleanable;
     private long handle;
     private final String libraryName;
     private final String libraryPath;