diff --git a/engine/runtime-parser-dsl/src/main/java/org/enso/runtime/parser/dsl/GenerateFields.java b/engine/runtime-parser-dsl/src/main/java/org/enso/runtime/parser/dsl/GenerateFields.java
index 25bd4c8b3222..05ff1f020be9 100644
--- a/engine/runtime-parser-dsl/src/main/java/org/enso/runtime/parser/dsl/GenerateFields.java
+++ b/engine/runtime-parser-dsl/src/main/java/org/enso/runtime/parser/dsl/GenerateFields.java
@@ -27,15 +27,11 @@
  * with {@link GenerateFields}. The parameter of the constructor can be one of the following:
  *
  * <ul>
- *   <li>Any reference, or primitive type without annotation
  *   <li>Any reference, or primitive type annotated with {@link IRField}
  *   <li>A subtype of {@code org.enso.compiler.ir.IR} annotated with {@link IRChild}
  *   <li>One of the <emph>meta</emph> types mentioned above
  * </ul>
  *
- * Constructor parameters without any annotation will not be processed at all. There will be no code
- * generated for them.
- *
  * <p>A user-defined field generated out of constructor parameter annotated with {@link IRChild} is
  * a child element of this IR element. That means that it will be included in generated
  * implementation of IR methods that iterate over the IR tree. For example {@code mapExpressions} or
@@ -47,6 +43,8 @@
  *
  * <p>For a constructor parameter of a meta type, there will be no user-defined field generated, as
  * the meta fields are always generated.
+ *
+ * <p>Other types of constructor parameters are forbidden.
  */
 @Retention(RetentionPolicy.SOURCE)
 @Target(ElementType.CONSTRUCTOR)
diff --git a/engine/runtime-parser-processor-tests/src/test/java/org/enso/runtime/parser/processor/test/TestIRProcessorInline.java b/engine/runtime-parser-processor-tests/src/test/java/org/enso/runtime/parser/processor/test/TestIRProcessorInline.java
index 404fde32ce07..7342ef2de465 100644
--- a/engine/runtime-parser-processor-tests/src/test/java/org/enso/runtime/parser/processor/test/TestIRProcessorInline.java
+++ b/engine/runtime-parser-processor-tests/src/test/java/org/enso/runtime/parser/processor/test/TestIRProcessorInline.java
@@ -3,6 +3,7 @@
 import static org.hamcrest.MatcherAssert.assertThat;
 import static org.hamcrest.Matchers.containsString;
 import static org.hamcrest.Matchers.is;
+import static org.junit.Assert.fail;
 
 import com.google.testing.compile.Compilation;
 import com.google.testing.compile.CompilationSubject;
@@ -46,7 +47,7 @@ private static void expectCompilationFailure(String src) {
     CompilationSubject.assertThat(compilation).failed();
   }
 
-  private static Compilation compile(String src, String name) {
+  private static Compilation compile(String name, String src) {
     var srcObject = JavaFileObjects.forSourceString(name, src);
     var compiler = Compiler.javac().withProcessors(new IRProcessor());
     var compilation = compiler.compile(srcObject);
@@ -194,6 +195,27 @@ public JName() {}
         containsString("protected JNameGen()"));
   }
 
+  @Test
+  public void annotatedConstructor_MustNotHaveUnannotatedParameters() {
+    var src =
+        """
+        import org.enso.runtime.parser.dsl.GenerateIR;
+        import org.enso.runtime.parser.dsl.GenerateFields;
+
+        @GenerateIR
+        public final class JName {
+          @GenerateFields
+          public JName(int param) {}
+        }
+        """;
+    try {
+      compile("JName", src);
+      fail("Exception in compilation expected");
+    } catch (Exception e) {
+      assertThat(e.getMessage(), containsString("must be annotated"));
+    }
+  }
+
   @Test
   public void annotatedConstructor_CanHaveMetaParameters() {
     var src =
diff --git a/engine/runtime-parser-processor/src/main/java/org/enso/runtime/parser/processor/field/FieldCollector.java b/engine/runtime-parser-processor/src/main/java/org/enso/runtime/parser/processor/field/FieldCollector.java
index ef0ce914ec2c..0d1b97797930 100644
--- a/engine/runtime-parser-processor/src/main/java/org/enso/runtime/parser/processor/field/FieldCollector.java
+++ b/engine/runtime-parser-processor/src/main/java/org/enso/runtime/parser/processor/field/FieldCollector.java
@@ -42,26 +42,21 @@ private void collectFromCtor() {
       var irFieldAnnot = param.getAnnotation(IRField.class);
       var irChildAnnot = param.getAnnotation(IRChild.class);
       Field field;
-      if (Utils.hasNoAnnotations(param)) {
-        field = null;
-      } else if (irFieldAnnot != null) {
+      if (irFieldAnnot != null) {
         field = processIrField(param, irFieldAnnot);
       } else if (irChildAnnot != null) {
         field = processIrChild(param, irChildAnnot);
       } else {
         var errMsg =
-            "Unexpected annotation on constructor parameter "
+            "Constructor parameter "
                 + param
-                + ". "
-                + "All annotations: "
-                + param.getAnnotationMirrors();
+                + " must be annotated with either @IRField or @IRChild";
         Utils.printError(errMsg, param, processingEnv.getMessager());
         throw new IllegalStateException(errMsg);
       }
 
-      if (field != null) {
-        fields.put(paramName, field);
-      }
+      assert field != null;
+      fields.put(paramName, field);
     }
   }