diff --git a/src/main.cc b/src/main.cc
index f022361d..88ea11a0 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -54,7 +54,7 @@ void register_env_vars()
             { return context.buffer().display_name(); }
         }, {
             "buffile",
-            [](StringView name, const Context& context)
+            [](StringView name, const Context& context) -> String
             { return context.buffer().name(); }
         }, {
             "buflist",
@@ -93,11 +93,11 @@ void register_env_vars()
             { return context.client().get_env_var(name.substr(11_byte)).str(); }
         }, {
             "session",
-            [](StringView name, const Context& context)
+            [](StringView name, const Context& context) -> String
             { return Server::instance().session(); }
         }, {
             "client",
-            [](StringView name, const Context& context)
+            [](StringView name, const Context& context) -> String
             { return context.name(); }
         }, {
             "cursor_line",
diff --git a/src/string.hh b/src/string.hh
index 1f622101..fba20f15 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -106,7 +106,7 @@ public:
     using Content = std::basic_string<char, std::char_traits<char>,
                                       Allocator<char, MemoryDomain::String>>;
 
-    String() = default;
+    String() {}
     String(const char* content) : m_data(content) {}
     explicit String(char content, CharCount count = 1) : m_data((size_t)(int)count, content) {}
     explicit String(Codepoint cp, CharCount count = 1)