diff --git a/mpact/sim/generic/arch_state.h b/mpact/sim/generic/arch_state.h
index 39549d6..30316ac 100644
--- a/mpact/sim/generic/arch_state.h
+++ b/mpact/sim/generic/arch_state.h
@@ -60,8 +60,8 @@
   ~ArchState() override;
 
  public:
-  using RegisterMap = absl::flat_hash_map<const std::string, RegisterBase *>;
-  using FifoMap = absl::flat_hash_map<const std::string, FifoBase *>;
+  using RegisterMap = absl::flat_hash_map<std::string, RegisterBase *>;
+  using FifoMap = absl::flat_hash_map<std::string, FifoBase *>;
 
   // Adds the given register to the register table.
   void AddRegister(RegisterBase *reg);
diff --git a/mpact/sim/util/memory/memory_router.h b/mpact/sim/util/memory/memory_router.h
index c655c46..a578ccb 100644
--- a/mpact/sim/util/memory/memory_router.h
+++ b/mpact/sim/util/memory/memory_router.h
@@ -46,9 +46,9 @@
  public:
   // Convenient map types shorthand.
   using InitiatorMap =
-      absl::flat_hash_map<const std::string, SingleInitiatorRouter *>;
+      absl::flat_hash_map<std::string, SingleInitiatorRouter *>;
   template <typename Interface>
-  using TargetMap = absl::flat_hash_map<const std::string, Interface *>;
+  using TargetMap = absl::flat_hash_map<std::string, Interface *>;
 
   MemoryRouter();
   MemoryRouter(const MemoryRouter &) = delete;