diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index a3c06fdae8e..3d605dc2340 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -7240,7 +7240,8 @@ make_rtl_for_nonlocal_decl (tree decl, tree init, const char* asmspec)
 		 This is horrible, as we're affecting a
 		 possibly-shared decl.  Again, a one-true-decl
 		 model breaks down.  */
-	      set_user_assembler_name (ns_decl, asmspec);
+	      if (ns_decl != error_mark_node)
+		set_user_assembler_name (ns_decl, asmspec);
 	}
     }
 
diff --git a/gcc/cp/name-lookup.c b/gcc/cp/name-lookup.c
index ef9fdddc86e..c9ac3db4d98 100644
--- a/gcc/cp/name-lookup.c
+++ b/gcc/cp/name-lookup.c
@@ -3477,7 +3477,9 @@ push_local_extern_decl_alias (tree decl)
 	  push_nested_namespace (ns);
 	  alias = do_pushdecl (alias, /* hiding= */true);
 	  pop_nested_namespace (ns);
-	  if (VAR_P (decl) && CP_DECL_THREAD_LOCAL_P (decl))
+	  if (VAR_P (decl)
+	      && CP_DECL_THREAD_LOCAL_P (decl)
+	      && alias != error_mark_node)
 	    set_decl_tls_model (alias, DECL_TLS_MODEL (decl));
 	}
     }
diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 40456a9dc5c..030341640e9 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -42359,7 +42359,8 @@ cp_parser_oacc_declare (cp_parser *parser, cp_token *pragma_tok)
 	       dependent local extern variable decls are as rare as
 	       hen's teeth.  */
 	    if (auto alias = DECL_LOCAL_DECL_ALIAS (decl))
-	      decl = alias;
+	      if (alias != error_mark_node)
+		decl = alias;
 
 	  if (OMP_CLAUSE_MAP_KIND (t) == GOMP_MAP_LINK)
 	    id = get_identifier ("omp declare target link");
@@ -43428,7 +43429,8 @@ cp_parser_omp_declare_target (cp_parser *parser, cp_token *pragma_tok)
       if (VAR_OR_FUNCTION_DECL_P (t)
 	  && DECL_LOCAL_DECL_P (t)
 	  && DECL_LANG_SPECIFIC (t)
-	  && DECL_LOCAL_DECL_ALIAS (t))
+	  && DECL_LOCAL_DECL_ALIAS (t)
+	  && DECL_LOCAL_DECL_ALIAS (t) != error_mark_node)
 	handle_omp_declare_target_clause (c, DECL_LOCAL_DECL_ALIAS (t),
 					  device_type);
     }
diff --git a/gcc/testsuite/g++.dg/tls/pr102642.C b/gcc/testsuite/g++.dg/tls/pr102642.C
new file mode 100644
index 00000000000..e3236d3dfdb
--- /dev/null
+++ b/gcc/testsuite/g++.dg/tls/pr102642.C
@@ -0,0 +1,10 @@
+// PR c++/102642
+// { dg-do compile { target c++11 } }
+
+thread_local int *z;		// { dg-message "previous declaration" }
+
+void
+foo ()
+{
+  extern thread_local int z;	// { dg-error "conflicting declaration" }
+}