diff --git a/core/src/main/java/de/redsix/dmncheck/validators/core/ValidationContext.java b/core/src/main/java/de/redsix/dmncheck/validators/core/ValidationContext.java
index 19ec082a..77b9f87c 100644
--- a/core/src/main/java/de/redsix/dmncheck/validators/core/ValidationContext.java
+++ b/core/src/main/java/de/redsix/dmncheck/validators/core/ValidationContext.java
@@ -18,7 +18,7 @@ public class ValidationContext {
 
     private static class Memoizer<T, U> {
 
-        private final Map<Class<T>, U> cache = new ConcurrentHashMap<>();
+        private final Map<Class<T>, @NonNull U> cache = new ConcurrentHashMap<>();
 
         private Function<Class<T>, U> doMemoize(final Function<Class<T>, @NonNull U> function) {
             return input -> cache.computeIfAbsent(input, function);
diff --git a/pom.xml b/pom.xml
index b1be7f97..bb4de5df 100644
--- a/pom.xml
+++ b/pom.xml
@@ -73,7 +73,7 @@
         <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
         <project.build.outputTimestamp>2023-01-01T00:00:00Z</project.build.outputTimestamp>
 
-        <checker.framework.version>3.42.0</checker.framework.version>
+        <checker.framework.version>3.48.0</checker.framework.version>
 
         <junit.version>5.11.1</junit.version>
         <mockito.version>5.14.1</mockito.version>
diff --git a/validators/checkerframework/stubs/jparsec.astub b/validators/checkerframework/stubs/jparsec.astub
new file mode 100644
index 00000000..5212a386
--- /dev/null
+++ b/validators/checkerframework/stubs/jparsec.astub
@@ -0,0 +1,5 @@
+import org.checkerframework.checker.regex.qual.Regex;
+package org.jparsec.pattern;
+public final class Patterns {
+  public static Pattern regex(@Regex String s);
+}
diff --git a/validators/checkerframework/stubs/jsonobject.astub b/validators/checkerframework/stubs/jsonobject.astub
new file mode 100644
index 00000000..da2ba380
--- /dev/null
+++ b/validators/checkerframework/stubs/jsonobject.astub
@@ -0,0 +1,6 @@
+import org.checkerframework.checker.nullness.qual.Nullable;
+package org.json;
+
+public class JSONObject {
+    public JSONObject put(String key, @Nullable Object value) throws JSONException;
+}