diff --git a/java-fast/io/nayuki/fastqrcodegen/Memoizer.java b/java-fast/io/nayuki/fastqrcodegen/Memoizer.java
index 34a50b7..1df5bc4 100644
--- a/java-fast/io/nayuki/fastqrcodegen/Memoizer.java
+++ b/java-fast/io/nayuki/fastqrcodegen/Memoizer.java
@@ -35,7 +35,7 @@ import java.util.function.Function;
 final class Memoizer<T,R> {
 	
 	private final Function<T,R> function;
-	Map<T,SoftReference<R>> cache = new ConcurrentHashMap<>();
+	private Map<T,SoftReference<R>> cache = new ConcurrentHashMap<>();
 	private Set<T> pending = new HashSet<>();