diff --git c/gcc/cp/module.cc w/gcc/cp/module.cc
index fab6b573d24..c87ddd16a80 100644
--- c/gcc/cp/module.cc
+++ w/gcc/cp/module.cc
@@ -3570,6 +3570,7 @@ class GTY((chain_next ("%h.parent"), for_user)) module_state {
 			 unsigned, unsigned *crc_ptr);
   bool read_namespaces (unsigned);
 
+  void intercluster_seed (trees_out &sec, unsigned index, depset *dep);
   unsigned write_cluster (elf_out *to, depset *depsets[], unsigned size,
 			  depset::hash &, unsigned *counts, unsigned *crc_ptr);
   bool read_cluster (unsigned snum);
@@ -8548,8 +8549,7 @@ trees_out::decl_node (tree decl, walk_kind ref)
 	gcc_checking_assert (index == ~import_entity_index (decl));
 
 #if CHECKING_P
-      if (importedness)
-	gcc_assert (!import == (importedness < 0));
+      gcc_assert (!import || importedness >= 0);
 #endif
       i (tt_entity);
       u (import);
@@ -14419,7 +14419,33 @@ enum ct_bind_flags
   cbf_wrapped = 0x8,  	/* ... that is wrapped.  */
 };
 
-/* Write the cluster of depsets in SCC[0-SIZE).  */
+/* DEP belongs to a different cluster, seed it to prevent
+   unfortunately timed duplicate import.  */
+// FIXME: QOI For inter-cluster references we could just only pick
+// one entity from an earlier cluster.  Even better track
+// dependencies between earlier clusters
+
+void
+module_state::intercluster_seed (trees_out &sec, unsigned index_hwm, depset *dep)
+{
+  if (dep->is_import ()
+      || dep->cluster < index_hwm)
+    {
+      tree ent = dep->get_entity ();
+      if (!TREE_VISITED (ent))
+	{
+	  sec.tree_node (ent);
+	  dump (dumper::CLUSTER)
+	    && dump ("Seeded %s %N",
+		     dep->is_import () ? "import" : "intercluster", ent);
+	}
+    }
+}
+
+/* Write the cluster of depsets in SCC[0-SIZE).
+   dep->section -> section number
+   dep->cluster -> entity number
+ */
 
 unsigned
 module_state::write_cluster (elf_out *to, depset *scc[], unsigned size,
@@ -14431,6 +14457,7 @@ module_state::write_cluster (elf_out *to, depset *scc[], unsigned size,
 
   trees_out sec (to, this, table, table.section);
   sec.begin ();
+  unsigned index_lwm = counts[MSC_entities];
 
   /* Determine entity numbers, mark for writing.   */
   dump (dumper::CLUSTER) && dump ("Cluster members:") && (dump.indent (), true);
@@ -14484,10 +14511,10 @@ module_state::write_cluster (elf_out *to, depset *scc[], unsigned size,
     }
   dump (dumper::CLUSTER) && (dump.outdent (), true);
 
-  /* Ensure every imported decl is referenced before we start
-     streaming.  This ensures that we never encounter the situation
-     where this cluster instantiates some implicit member that
-     importing some other decl causes to be instantiated.  */
+  /* Ensure every out-of-cluster decl is referenced before we start
+     streaming.  We must do both imports *and* earlier clusters,
+     because the latter could reach into the former and cause a
+     duplicate loop.   */
   sec.set_importing (+1);
   for (unsigned ix = 0; ix != size; ix++)
     {
@@ -14505,30 +14532,14 @@ module_state::write_cluster (elf_out *to, depset *scc[], unsigned size,
 		  depset *bind = dep->deps[ix];
 		  if (bind->get_entity_kind () == depset::EK_USING)
 		    bind = bind->deps[1];
-		  if (bind->is_import ())
-		    {
-		      tree import = bind->get_entity ();
-		      if (!TREE_VISITED (import))
-			{
-			  sec.tree_node (import);
-			  dump (dumper::CLUSTER)
-			    && dump ("Seeded import %N", import);
-			}
-		    }
+
+		  intercluster_seed (sec, index_lwm, bind);
 		}
 	      /* Also check the namespace itself.  */
 	      dep = dep->deps[0];
 	    }
 
-	  if (dep->is_import ())
-	    {
-	      tree import = dep->get_entity ();
-	      if (!TREE_VISITED (import))
-		{
-		  sec.tree_node (import);
-		  dump (dumper::CLUSTER) && dump ("Seeded import %N", import);
-		}
-	    }
+	  intercluster_seed (sec, index_lwm, dep);
 	}
     }
   sec.tree_node (NULL_TREE);
diff --git c/gcc/testsuite/g++.dg/modules/hdr-init-1_c.C w/gcc/testsuite/g++.dg/modules/hdr-init-1_c.C
index efcc4854314..2a103c3d0bb 100644
--- c/gcc/testsuite/g++.dg/modules/hdr-init-1_c.C
+++ w/gcc/testsuite/g++.dg/modules/hdr-init-1_c.C
@@ -17,8 +17,8 @@ int main ()
 
 // { dg-final { scan-lang-dump-times {Reading 1 initializers} 2 module } }
 
-// { dg-final { scan-lang-dump {Read:-1's named merge key \(new\) var_decl:'::var'} module } }
+// { dg-final { scan-lang-dump {Read:-[0-9]*'s named merge key \(new\) var_decl:'::var'} module } }
 // { dg-final { scan-lang-dump-times {Reading definition var_decl '::var@[^\n]*/hdr-init-1_a.H:1'} 2 module } }
 
-// { dg-final { scan-lang-dump {Read:-1's named merge key \(matched\) var_decl:'::var'} module } }
+// { dg-final { scan-lang-dump {Read:-[0-9]*'s named merge key \(matched\) var_decl:'::var'} module } }
 
diff --git c/gcc/testsuite/g++.dg/modules/indirect-3_c.C w/gcc/testsuite/g++.dg/modules/indirect-3_c.C
index 9c5cb230ad2..ec2fc768373 100644
--- c/gcc/testsuite/g++.dg/modules/indirect-3_c.C
+++ w/gcc/testsuite/g++.dg/modules/indirect-3_c.C
@@ -19,6 +19,6 @@ int main ()
 // { dg-final { scan-lang-dump-not {Instantiation:-[0-9]* function_decl:'::foo::X@foo:.::frob@.()<0x0>'} module } }
 
 // { dg-final { scan-lang-dump {Lazily binding '::bar@bar:.::toto'@'bar' section:} module } }
-// { dg-final { scan-lang-dump {>Loading entity foo\[1\] section:1} module } }
+// { dg-final { scan-lang-dump {>Loading entity foo\[.\] section:1} module } }
 // { dg-final { scan-lang-dump {Imported:-[0-9]* template_decl:'::foo@foo:.::template TPL@foo:.'@foo} module } }
 // { dg-final { scan-lang-dump {Reading definition type_decl '::foo@foo:.::TPL@bar:.<0x0>'} module } }
diff --git c/gcc/testsuite/g++.dg/modules/indirect-4_c.C w/gcc/testsuite/g++.dg/modules/indirect-4_c.C
index 7efcc115e71..d55a2216fb3 100644
--- c/gcc/testsuite/g++.dg/modules/indirect-4_c.C
+++ w/gcc/testsuite/g++.dg/modules/indirect-4_c.C
@@ -10,7 +10,7 @@ int main ()
 }
 
 // { dg-final { scan-lang-dump {Lazily binding '::bar@bar:.::quux'@'bar' section:} module } }
-// { dg-final { scan-lang-dump {>Loading entity foo\[2\] section:1} module } }
+// { dg-final { scan-lang-dump {>Loading entity foo\[.\] section:1} module } }
 // { dg-final { scan-lang-dump {Imported:-[0-9]* template_decl:'::foo@foo:.::template TPL@foo:.'@foo} module } }
 
 // { dg-final { scan-lang-dump {Reading definition function_decl '::foo@foo:.::TPL@bar:.<0x1>::frob@bar:.<0x2>'} module } }
diff --git c/gcc/testsuite/g++.dg/modules/lambda-3_b.C w/gcc/testsuite/g++.dg/modules/lambda-3_b.C
index 25a418bb44a..17afd967745 100644
--- c/gcc/testsuite/g++.dg/modules/lambda-3_b.C
+++ w/gcc/testsuite/g++.dg/modules/lambda-3_b.C
@@ -4,6 +4,6 @@
 import "lambda-3_a.H";
 
 // { dg-final { scan-lang-dump-not {merge key \(new\)} module } }
-// { dg-final { scan-lang-dump {Read -1\[0\] matched attached decl '::template ._anon_0<#unnamed#>'} module } }
-// { dg-final { scan-lang-dump {Read -1\[0\] matched attached decl '::._anon_2'} module } }
-// { dg-final { scan-lang-dump {Read -1\[0\] matched attached decl '::._anon_1'} module } }
+// { dg-final { scan-lang-dump {Read -[0-9]*\[0\] matched attached decl '::template ._anon_0<#unnamed#>'} module } }
+// { dg-final { scan-lang-dump {Read -[0-9]*\[0\] matched attached decl '::._anon_2'} module } }
+// { dg-final { scan-lang-dump {Read -[0-9]*\[0\] matched attached decl '::._anon_1'} module } }
diff --git c/gcc/testsuite/g++.dg/modules/late-ret-3_c.C w/gcc/testsuite/g++.dg/modules/late-ret-3_c.C
index fae956542f9..8ab23a9e338 100644
--- c/gcc/testsuite/g++.dg/modules/late-ret-3_c.C
+++ w/gcc/testsuite/g++.dg/modules/late-ret-3_c.C
@@ -19,4 +19,4 @@ int main ()
   return 0;
 }
 
-// { dg-final { scan-lang-dump {Read:-1's named merge key \(matched\) template_decl:'::template Foo'\n  Deduping '::template Foo@[^\n]*/late-ret-3_a.H:.'\n} module } }
+// { dg-final { scan-lang-dump {Read:-[0-9]*'s named merge key \(matched\) template_decl:'::template Foo'\n  Deduping '::template Foo@[^\n]*/late-ret-3_a.H:.'\n} module } }
diff --git c/gcc/testsuite/g++.dg/modules/pr99283-6.h w/gcc/testsuite/g++.dg/modules/pr99283-6.h
new file mode 100644
index 00000000000..383b66c081e
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99283-6.h
@@ -0,0 +1,23 @@
+template<bool, typename, typename>
+struct conditional;
+
+template<typename> struct incrementable_traits;
+
+template<typename _Iter, typename _Tp>
+struct __iter_traits_impl;
+
+class __max_diff_type;
+
+template<typename _Iter>
+concept weakly_incrementable
+  =  __is_same (__iter_traits_impl<_Iter, incrementable_traits<_Iter>>,
+		__max_diff_type);
+
+template<typename _Iterator>
+class reverse_iterator
+{
+public:
+  using iterator_concept
+    = typename conditional<weakly_incrementable<_Iterator>,
+			   int, int>::type;
+};
diff --git c/gcc/testsuite/g++.dg/modules/pr99283-6_a.H w/gcc/testsuite/g++.dg/modules/pr99283-6_a.H
new file mode 100644
index 00000000000..176ad9e9e8c
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99283-6_a.H
@@ -0,0 +1,33 @@
+// { dg-additional-options {-std=c++2a -fmodule-header} }
+// { dg-module-cmi {}
+
+#include "pr99283-6.h"
+
+template<typename _IteratorL, typename _IteratorR>
+constexpr bool
+  operator<(const reverse_iterator<_IteratorL>& __x,
+	    const reverse_iterator<_IteratorR>& __y);
+
+template<typename _Tp>
+  struct numeric_limits;
+
+class __max_size_type
+{
+public:
+  template<typename _Tp>
+  constexpr
+    __max_size_type(_Tp __i) noexcept
+      : _M_val(__i), _M_msb(__i < 0)
+  { }
+
+  using __rep = __UINT64_TYPE__;
+private:
+  __rep _M_val = 0;
+  unsigned _M_msb:1 = 0;
+};
+
+class __max_diff_type
+{
+private:
+  __max_size_type _M_rep = 0;
+};
diff --git c/gcc/testsuite/g++.dg/modules/pr99283-6_b.H w/gcc/testsuite/g++.dg/modules/pr99283-6_b.H
new file mode 100644
index 00000000000..123f3534673
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99283-6_b.H
@@ -0,0 +1,164 @@
+// { dg-additional-options {-std=c++2a -fmodule-header} }
+// { dg-module-cmi {}
+
+#include "pr99283-6.h"
+
+template<typename _Tp>
+void __addressof(_Tp& __r)  ;
+
+template<typename _Tp, _Tp __v>
+struct integral_constant
+{
+  static constexpr _Tp value = __v;
+};
+
+template<typename _Tp, _Tp __v>
+constexpr _Tp integral_constant<_Tp, __v>::value;
+
+typedef integral_constant<bool, true> true_type;
+typedef integral_constant<bool, false> false_type;
+
+template<typename _B1, typename _B2>
+struct __and_
+  : public conditional<_B1::value, _B2, _B1>::type
+{ };
+
+template<typename _From, typename _To>
+struct is_convertible
+  : public true_type
+{ };
+
+template<bool, typename _Tp = void>
+struct enable_if
+{ };
+
+template<typename _Tp>
+struct enable_if<true, _Tp>
+{ typedef _Tp type; };
+
+template<bool _Cond, typename _Tp = void>
+using __enable_if_t = typename enable_if<_Cond, _Tp>::type;
+
+template<typename A, typename B>
+using _Require = __enable_if_t<__and_<A, B>::value>;
+
+template<bool _Cond, typename _Iftrue, typename _Iffalse>
+struct conditional
+{ typedef _Iftrue type; };
+
+template<typename> struct iterator_traits;
+
+
+template<typename _IteratorL, typename _IteratorR>
+constexpr bool
+  operator!=(const reverse_iterator<_IteratorL>& __x,
+	     const reverse_iterator<_IteratorR>& __y);
+
+typedef __INT64_TYPE__ int64_t;
+typedef int64_t intmax_t;
+
+template<intmax_t _Num>
+struct ratio
+{
+};
+
+namespace chrono
+{
+template<typename _Rep>
+struct duration;
+
+template<typename _ToDur, typename _Rep>
+constexpr _ToDur
+  duration_cast(const duration<_Rep>& __d)
+{
+  typedef typename _ToDur::rep __to_rep;
+  return _ToDur(static_cast<__to_rep>(static_cast<intmax_t>(__d.count())));
+}
+
+template<typename _Rep>
+struct duration
+{
+  
+public:
+  using rep = _Rep;
+  
+  constexpr duration() = default;
+
+  duration(const duration&) = default;
+
+  template<typename _Rep2, typename
+	   = _Require<is_convertible<const _Rep2&, rep>,
+		      true_type>>
+  constexpr explicit duration(const _Rep2& __rep)
+    : __r (__rep) {}
+  
+  ~duration() = default;
+  duration& operator=(const duration&) = default;
+
+  rep count() const;
+  
+private:
+  rep __r;
+};
+
+using seconds = duration<int64_t>;
+
+template<typename _Clock, typename _Dur>
+struct time_point
+{
+  typedef _Dur duration;
+
+  duration time_since_epoch() const;
+
+private:
+  duration __d;
+};
+
+struct system_clock
+{
+  typedef chrono::seconds duration;
+	 
+  typedef chrono::time_point<system_clock, duration> time_point;
+
+  static void
+    to_time_t(const time_point& __t) noexcept
+  {
+    duration_cast<chrono::seconds>
+     (__t.time_since_epoch()).count();
+  }
+};
+
+}
+
+template<typename>
+class allocator;
+
+template<typename _ForwardIterator>
+constexpr void
+  __destroy(_ForwardIterator __first, _ForwardIterator __last)
+{
+  for (; __first != __last; ++__first)
+    __addressof (*__first);
+}
+
+template<typename _Alloc>
+struct allocator_traits
+{
+private:
+  template<typename _Alloc2, typename _Tp>
+  static constexpr void
+    _S_destroy(_Alloc2&, _Tp* __p, ...)
+    noexcept
+  {
+    __destroy(__p);
+  }
+};
+
+template<typename _Tp>
+struct allocator_traits<allocator<_Tp>>
+{
+  using value_type = _Tp;
+  using pointer = _Tp*;
+};
+
+import "pr99283-6_a.H";
diff --git c/gcc/testsuite/g++.dg/modules/pr99283-6_c.C w/gcc/testsuite/g++.dg/modules/pr99283-6_c.C
new file mode 100644
index 00000000000..9492554617d
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99283-6_c.C
@@ -0,0 +1,10 @@
+// { dg-additional-options {-std=c++2a -fmodules-ts} }
+
+import  "pr99283-6_b.H";
+
+template<typename _Alloc>
+struct __allocated_ptr
+{
+  using value_type = allocator_traits<_Alloc>;
+};
+
diff --git c/gcc/testsuite/g++.dg/modules/pr99425-1_b.H w/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
index 98303a0c687..53d28b4ef5e 100644
--- c/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
+++ w/gcc/testsuite/g++.dg/modules/pr99425-1_b.H
@@ -15,5 +15,5 @@ inline void widget (Cont parm)
   ssize (parm);
 }
 
-// { dg-final { scan-lang-dump {Read:-[0-9]*'s alias spec merge key \(new\) type_decl:'::make_signed_t'\n  ...  Read:-[0-9]*'s type spec merge key \(new\) type_decl:'::make_signed'\n  Read:-1's named merge key \(matched\) template_decl:'::template ssize'} module } }
+// { dg-final { scan-lang-dump {Read:-[0-9]*'s alias spec merge key \(new\) type_decl:'::make_signed_t'\n  ...  Read:-[0-9]*'s type spec merge key \(new\) type_decl:'::make_signed'\n  Read:-[0-9]*'s named merge key \(matched\) template_decl:'::template ssize'} module } }
 
diff --git c/gcc/testsuite/g++.dg/modules/pr99425-1_c.C w/gcc/testsuite/g++.dg/modules/pr99425-1_c.C
index 28ef3a1ff30..77a35a88b39 100644
--- c/gcc/testsuite/g++.dg/modules/pr99425-1_c.C
+++ w/gcc/testsuite/g++.dg/modules/pr99425-1_c.C
@@ -7,5 +7,5 @@ void frob (Cont parm)
   ssize (parm);
 }
 
-// { dg-final { scan-lang-dump {Read:-1's named merge key \(new\) template_decl:'::template ssize'} module } }
-// { dg-final { scan-lang-dump {Read:-1's named merge key \(matched\) template_decl:'::template ssize'} module } }
+// { dg-final { scan-lang-dump {Read:-[0-9]*'s named merge key \(new\) template_decl:'::template ssize'} module } }
+// { dg-final { scan-lang-dump {Read:-[0-9]*'s named merge key \(matched\) template_decl:'::template ssize'} module } }