@@ -139,7 +139,11 @@ private InnerInterpolator createInterpolator(
                 return di.interpolate(value, null, cycleMap, cb, postprocessor, false);
             } catch (InterpolatorException e) {
                 problems.add(BuilderProblem.Severity.ERROR, ModelProblem.Version.BASE, e.getMessage(), e);
-                return null;
+                // Keep the original text rather than handing null back to the transformer. A null
+                // ends up as an element of a List<String> model field such as build/filters, and
+                // the immutable model constructor copies that list with List.copyOf, which fails
+                // with a bare NullPointerException that hides the problem just collected above.
+                return value;
             }
         };
     }
 
@@ -632,6 +632,26 @@ public void testRecursiveExpressionCycleNPE() throws Exception {
         assertTrue(collector.getErrors().get(0).contains("recursive variable reference"));
     }
 
+    @Test
+    public void testRecursiveExpressionCycleInListField() throws Exception {
+        Map<String, String> props = new HashMap<>();
+        props.put("aa", "${bb}");
+        props.put("bb", "${aa}");
+
+        Model model = Model.newBuilder()
+                .properties(props)
+                .build(Build.newBuilder().filters(List.of("${aa}")).build())
+                .build();
+
+        SimpleProblemCollector collector = new SimpleProblemCollector();
+
+        ModelBuilderRequest request = createModelBuildingRequest(Map.of()).build();
+        Model out = interpolator.interpolateModel(model, null, request, collector);
+
+        assertEquals(List.of("${aa}"), out.getBuild().getFilters());
+        assertTrue(collector.getErrors().get(0).contains("recursive variable reference"));
+    }
+
     @Disabled("per def cannot be recursive: ${basedir} is immediately going for project.basedir")
     @Test
     public void testRecursiveExpressionCycleBaseDir() throws Exception {
Original file line number	Diff line number	Diff line change
`@@ -139,7 +139,11 @@ private InnerInterpolator createInterpolator(`
`139`	`139`	`return di.interpolate(value, null, cycleMap, cb, postprocessor, false);`
`140`	`140`	`} catch (InterpolatorException e) {`
`141`	`141`	`problems.add(BuilderProblem.Severity.ERROR, ModelProblem.Version.BASE, e.getMessage(), e);`
`142`		`- return null;`
	`142`	`+ // Keep the original text rather than handing null back to the transformer. A null`
	`143`	`+ // ends up as an element of a List<String> model field such as build/filters, and`
	`144`	`+ // the immutable model constructor copies that list with List.copyOf, which fails`
	`145`	`+ // with a bare NullPointerException that hides the problem just collected above.`
	`146`	`+ return value;`
`143`	`147`	`}`
`144`	`148`	`};`
`145`	`149`	`}`