diff --git a/core/src/main/java/ai/timefold/solver/core/impl/domain/variable/declarative/PathPartIterator.java b/core/src/main/java/ai/timefold/solver/core/impl/domain/variable/declarative/PathPartIterator.java
index af2f1b828c4..f4e6981aa77 100644
--- a/core/src/main/java/ai/timefold/solver/core/impl/domain/variable/declarative/PathPartIterator.java
+++ b/core/src/main/java/ai/timefold/solver/core/impl/domain/variable/declarative/PathPartIterator.java
@@ -4,6 +4,7 @@
 import java.lang.reflect.Method;
 import java.lang.reflect.Type;
 import java.util.Iterator;
+import java.util.NoSuchElementException;
 
 import ai.timefold.solver.core.config.util.ConfigUtils;
 import ai.timefold.solver.core.preview.api.domain.variable.declarative.ShadowSources;
@@ -28,6 +29,9 @@ public boolean hasNext() {
 
     @Override
     public PathPart next() {
+        if (!hasNext()) {
+            throw new NoSuchElementException();
+        }
         var index = previous.index() + 1;
         var name = parts[index];
         var isCollection = false;
diff --git a/python/jpyinterpreter/src/main/java/ai/timefold/jpyinterpreter/PythonClassTranslator.java b/python/jpyinterpreter/src/main/java/ai/timefold/jpyinterpreter/PythonClassTranslator.java
index 573ef946d8d..79d598de2d9 100644
--- a/python/jpyinterpreter/src/main/java/ai/timefold/jpyinterpreter/PythonClassTranslator.java
+++ b/python/jpyinterpreter/src/main/java/ai/timefold/jpyinterpreter/PythonClassTranslator.java
@@ -1593,7 +1593,13 @@ public static InterfaceDeclaration getInterfaceForInstancePythonFunction(String
             pythonParameterTypes[0] = 'L' + instanceInternalClassName + ';';
         }
 
-        for (int i = 1; i < pythonCompiledFunction.totalArgCount(); i++) {
+        return getInterfaceDeclaration(pythonCompiledFunction, parameterPythonTypeList, pythonParameterTypes);
+    }
+
+    private static PythonClassTranslator.InterfaceDeclaration getInterfaceDeclaration(
+            PythonCompiledFunction pythonCompiledFunction, List<PythonLikeType> parameterPythonTypeList,
+            String[] pythonParameterTypes) {
+        for (int i = 1; i < pythonParameterTypes.length; i++) {
             pythonParameterTypes[i] = 'L' + parameterPythonTypeList.get(i).getJavaTypeInternalName() + ';';
         }
         String returnType = 'L' + pythonCompiledFunction.getReturnType().map(PythonLikeType::getJavaTypeInternalName)
@@ -1611,14 +1617,7 @@ public static InterfaceDeclaration getInterfaceForClassPythonFunction(PythonComp
             pythonParameterTypes[0] = Type.getDescriptor(PythonLikeType.class);
         }
 
-        for (int i = 1; i < pythonCompiledFunction.totalArgCount(); i++) {
-            pythonParameterTypes[i] = 'L' + parameterPythonTypeList.get(i).getJavaTypeInternalName() + ';';
-        }
-        String returnType = 'L' + pythonCompiledFunction.getReturnType().map(PythonLikeType::getJavaTypeInternalName)
-                .orElseGet(() -> getPythonReturnTypeOfFunction(pythonCompiledFunction, true).getJavaTypeInternalName()) + ';';
-        FunctionSignature functionSignature = new FunctionSignature(returnType, pythonParameterTypes);
-        return functionSignatureToInterfaceName.computeIfAbsent(functionSignature,
-                PythonClassTranslator::createInterfaceForFunctionSignature);
+        return getInterfaceDeclaration(pythonCompiledFunction, parameterPythonTypeList, pythonParameterTypes);
     }
 
     public static InterfaceDeclaration createInterfaceForFunctionSignature(FunctionSignature functionSignature) {