diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTNode.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTNode.java
index 145fa18a699..f840a8daf7f 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTNode.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTNode.java
@@ -16,7 +16,10 @@ import org.eclipse.cdt.core.parser.IToken;
 /**
  * This is the root node in the physical AST. A physical node represents a chunk
  * of text in the source program.
- * 
+ *
+ * Classes implementing this interface are not thread safe.
+ * Even 'get' methods may cause changes to the underlying object.
+ *
  * @noimplement This interface is not intended to be implemented by clients.
  * @noextend This interface is not intended to be extended by clients.
  */
diff --git a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTTranslationUnit.java b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTTranslationUnit.java
index 6226a856945..5471d9406c8 100644
--- a/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTTranslationUnit.java
+++ b/core/org.eclipse.cdt.core/parser/org/eclipse/cdt/core/dom/ast/IASTTranslationUnit.java
@@ -20,7 +20,10 @@ import org.eclipse.core.runtime.IAdaptable;
 
 /**
  * The translation unit represents a compilable unit of source.
- * 
+ *
+ * All existing implementations of IASTTranslationUnit are not thread safe.
+ * Even 'get' methods may cause changes to the underlying object.
+ *
  * @noextend This interface is not intended to be extended by clients.
  * @noimplement This interface is not intended to be implemented by clients.
  */