diff --git a/shared/src/main/scala/io/kaitai/struct/format/ClassSpec.scala b/shared/src/main/scala/io/kaitai/struct/format/ClassSpec.scala
index 580c37dd7..f76559e9f 100644
--- a/shared/src/main/scala/io/kaitai/struct/format/ClassSpec.scala
+++ b/shared/src/main/scala/io/kaitai/struct/format/ClassSpec.scala
@@ -78,6 +78,14 @@ case class ClassSpec(
 
   def parentType: DataType = parentClass.toDataType
 
+  /**
+   * Determines whether this `ClassSpec` represents a type that is external
+   * (i.e. not defined in the same .ksy file) from the perspective of the given
+   * `ClassSpec`.
+   */
+  def isExternal(curClass: ClassSpec): Boolean =
+    name.head != curClass.name.head
+
   /**
     * Recursively traverses tree of types starting from this type, calling
     * certain function for every type, starting from this one.
diff --git a/shared/src/main/scala/io/kaitai/struct/precompile/ParentTypes.scala b/shared/src/main/scala/io/kaitai/struct/precompile/ParentTypes.scala
index 288267786..c6c002352 100644
--- a/shared/src/main/scala/io/kaitai/struct/precompile/ParentTypes.scala
+++ b/shared/src/main/scala/io/kaitai/struct/precompile/ParentTypes.scala
@@ -68,7 +68,6 @@ class ParentTypes(classSpecs: ClassSpecs) {
   }
 
   def markupParentAs(curClass: ClassSpec, ut: UserType): Unit = {
-    Log.typeProcParent.info(() => s"..... class=$ut has parent=${curClass.nameAsStr}")
     ut.classSpec match {
       case Some(usedClass) =>
         markupParentAs(curClass, usedClass)
@@ -79,6 +78,10 @@ class ParentTypes(classSpecs: ClassSpecs) {
   }
 
   def markupParentAs(parent: ClassSpec, child: ClassSpec): Unit = {
+    // Don't allow type usages across spec boundaries to affect parent resolution
+    if (child.isExternal(parent))
+      return
+    Log.typeProcParent.info(() => s"..... class=${child.nameAsStr} has parent=${parent.nameAsStr}")
     child.parentClass match {
       case UnknownClassSpec =>
         child.parentClass = parent