Index: clang/include/clang/AST/DeclTemplate.h
===================================================================
--- clang/include/clang/AST/DeclTemplate.h
+++ clang/include/clang/AST/DeclTemplate.h
@@ -15,6 +15,7 @@
 #define LLVM_CLANG_AST_DECLTEMPLATE_H
 
 #include "clang/AST/ASTConcept.h"
+#include "clang/AST/ASTContext.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclBase.h"
 #include "clang/AST/DeclCXX.h"
@@ -373,11 +374,19 @@
 
   /// Set that the default argument was inherited from another parameter.
   void setInherited(const ASTContext &C, ParmDecl *InheritedFrom) {
-    assert(!isInherited() && "default argument already inherited");
     InheritedFrom = getParmOwningDefaultArg(InheritedFrom);
     if (!isSet())
       ValueOrInherited = InheritedFrom;
-    else
+    else if (auto *D = ValueOrInherited.template dyn_cast<ParmDecl *>()) {
+      assert(C.isSameDefaultTemplateArgument(D, InheritedFrom));
+      ValueOrInherited =
+          new (allocateDefaultArgStorageChain(C)) Chain{InheritedFrom, get()};
+    } else if (auto *Inherited =
+                   ValueOrInherited.template dyn_cast<Chain *>()) {
+      assert(C.isSameDefaultTemplateArgument(Inherited->PrevDeclWithDefaultArg,
+                                             InheritedFrom));
+      Inherited->PrevDeclWithDefaultArg = InheritedFrom;
+    } else
       ValueOrInherited = new (allocateDefaultArgStorageChain(C))
           Chain{InheritedFrom, ValueOrInherited.template get<ArgType>()};
   }
Index: clang/test/Modules/InheritDefaultArguments.cppm
===================================================================
--- clang/test/Modules/InheritDefaultArguments.cppm
+++ clang/test/Modules/InheritDefaultArguments.cppm
@@ -10,7 +10,10 @@
 class Templ;
 
 template <typename T, typename U>
-class Templ {};
+class Templ {
+public:
+    Templ(T t) {}
+};
 
 template <typename T>
 Templ(T t) -> Templ<T, int>;
@@ -26,3 +29,6 @@
 #include "foo.h"
 export module X;
 import A;
+void foo() {
+    Templ t(0);
+}
Index: clang/test/Modules/Inputs/PR31469/textual.h
===================================================================
--- clang/test/Modules/Inputs/PR31469/textual.h
+++ clang/test/Modules/Inputs/PR31469/textual.h
@@ -4,7 +4,7 @@
   template <class _Tp> class allocator;
   template <class _Tp, class _Alloc = allocator<_Tp>> class list;
   template <class _VoidPtr> class __list_iterator {
-    //template <class> friend class list; // causes another crash in ASTDeclReader::attachPreviousDecl
+    template <class> friend class list;
     template <class, class> friend class list;
   };
   template <class _Tp, class _Alloc> class __list_imp {};