diff --git a/src/interned_string.cc b/src/interned_string.cc
index b949233f..1a7b5627 100644
--- a/src/interned_string.cc
+++ b/src/interned_string.cc
@@ -40,7 +40,7 @@ void StringRegistry::acquire(size_t slot)
     ++m_storage[slot].second;
 }
 
-void StringRegistry::release(size_t slot)
+void StringRegistry::release(size_t slot) noexcept
 {
     if (--m_storage[slot].second == 0)
     {
diff --git a/src/interned_string.hh b/src/interned_string.hh
index 23eeab92..43df5fb4 100644
--- a/src/interned_string.hh
+++ b/src/interned_string.hh
@@ -18,7 +18,7 @@ private:
 
     InternedString acquire(StringView str);
     void acquire(size_t slot);
-    void release(size_t slot);
+    void release(size_t slot) noexcept;
 
     std::unordered_map<StringView, size_t> m_slot_map;
     std::vector<size_t> m_free_slots;
@@ -62,8 +62,10 @@ public:
         return *this;
     }
 
-    InternedString& operator=(InternedString&& str)
+    InternedString& operator=(InternedString&& str) noexcept
     {
+        release_ifn();
+
         static_cast<StringView&>(*this) = str;
         m_slot = str.m_slot;
         str.m_slot = -1;
@@ -110,7 +112,7 @@ private:
             *this = StringRegistry::instance().acquire(str);
     }
 
-    void release_ifn()
+    void release_ifn() noexcept
     {
         if (m_slot != -1)
             StringRegistry::instance().release(m_slot);
diff --git a/src/optional.hh b/src/optional.hh
index 68277b1a..3f919043 100644
--- a/src/optional.hh
+++ b/src/optional.hh
@@ -20,6 +20,7 @@ public:
     }
 
     Optional(Optional&& other)
+        noexcept(noexcept(new ((void*)0) T(std::move(other.m_value))))
         : m_valid(other.m_valid)
     {
         if (m_valid)
diff --git a/src/safe_ptr.hh b/src/safe_ptr.hh
index 6a53a02e..ac3af21d 100644
--- a/src/safe_ptr.hh
+++ b/src/safe_ptr.hh
@@ -29,7 +29,7 @@ public:
         #endif
     }
     safe_ptr(const safe_ptr& other) : safe_ptr(other.m_ptr) {}
-    safe_ptr(safe_ptr&& other) : m_ptr(other.m_ptr)
+    safe_ptr(safe_ptr&& other) noexcept : m_ptr(other.m_ptr)
     {
         other.m_ptr = nullptr;
         #ifdef KAK_DEBUG
@@ -60,7 +60,7 @@ public:
         return *this;
     }
 
-    safe_ptr& operator=(safe_ptr&& other)
+    safe_ptr& operator=(safe_ptr&& other) noexcept
     {
         #ifdef KAK_DEBUG
         if (m_ptr)