diff --git a/toolchain/sem_ir/name_scope.h b/toolchain/sem_ir/name_scope.h
index 34a771d1ff96..48af6fd157d7 100644
--- a/toolchain/sem_ir/name_scope.h
+++ b/toolchain/sem_ir/name_scope.h
@@ -138,7 +138,7 @@ class NameScope : public Printable<NameScope> {
 
   // Disallow copy, allow move.
   NameScope(NameScope&& other) = default;
-  auto operator=(NameScope&& other) -> NameScope& = default;
+  auto operator=(NameScope&& other) noexcept -> NameScope& = default;
 
   explicit NameScope(InstId inst_id, NameId name_id,
                      NameScopeId parent_scope_id)