diff --git a/src/buffer_manager.cc b/src/buffer_manager.cc
index 09ee1aca..43aa2f58 100644
--- a/src/buffer_manager.cc
+++ b/src/buffer_manager.cc
@@ -86,7 +86,7 @@ Buffer& BufferManager::get_buffer(StringView name)
 {
     Buffer* res = get_buffer_ifp(name);
     if (not res)
-        throw runtime_error("no such buffer '"_str + name + "'");
+        throw runtime_error(format("no such buffer '{}'", name));
     return *res;
 }
 
diff --git a/src/file.cc b/src/file.cc
index bc68e6f1..adbb37cc 100644
--- a/src/file.cc
+++ b/src/file.cc
@@ -28,7 +28,7 @@ String parse_filename(StringView filename)
 {
     if (filename.length() >= 1 and filename[0_byte] == '~' and
         (filename.length() == 1 or filename[1_byte] == '/'))
-        return parse_filename("$HOME"_str + filename.substr(1_byte));
+        return parse_filename("$HOME" + filename.substr(1_byte));
 
     ByteCount pos = 0;
     String result;
diff --git a/src/highlighter_group.cc b/src/highlighter_group.cc
index ecaafa95..8a9d364f 100644
--- a/src/highlighter_group.cc
+++ b/src/highlighter_group.cc
@@ -31,7 +31,7 @@ Highlighter& HighlighterGroup::get_child(StringView path)
     StringView id(path.begin(), sep_it);
     auto it = m_highlighters.find(id);
     if (it == m_highlighters.end())
-        throw child_not_found("no such id: "_str + id);
+        throw child_not_found("no such id: " + id);
     if (sep_it == path.end())
         return *it->second;
     else
diff --git a/src/highlighters.cc b/src/highlighters.cc
index aa1e09eb..a7e5b47a 100644
--- a/src/highlighters.cc
+++ b/src/highlighters.cc
@@ -1150,7 +1150,7 @@ public:
         StringView id(path.begin(), sep_it);
         auto it = m_groups.find(id);
         if (it == m_groups.end())
-            throw child_not_found("no such id: "_str + id);
+            throw child_not_found(format("no such id: {}", id));
         if (sep_it == path.end())
             return it->second;
         else
diff --git a/src/main.cc b/src/main.cc
index 7c7dc86d..b38ccc26 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -390,12 +390,12 @@ int run_server(StringView session, StringView init_command,
     if (not ignore_kakrc) try
     {
         Context initialisation_context{Context::EmptyContextFlag{}};
-        command_manager.execute("source " + runtime_directory() + "/kakrc",
+        command_manager.execute(format("source {}/kakrc", runtime_directory()),
                                 initialisation_context);
     }
     catch (Kakoune::runtime_error& error)
     {
-        write_debug("error while parsing kakrc:\n    "_str + error.what());
+        write_debug(format("error while parsing kakrc:\n    {}", error.what()));
     }
     catch (Kakoune::client_removed&)
     {
@@ -419,7 +419,7 @@ int run_server(StringView session, StringView init_command,
     }
     catch (Kakoune::runtime_error& error)
     {
-         write_debug("error while opening command line files: "_str + error.what());
+         write_debug(format("error while opening command line files: {}", error.what()));
     }
     else
         new Buffer("*scratch*", Buffer::Flags::None);
diff --git a/src/normal.cc b/src/normal.cc
index 6ca83ab2..ef4231bf 100644
--- a/src/normal.cc
+++ b/src/normal.cc
@@ -585,14 +585,14 @@ void regex_prompt(Context& context, const String prompt, T func)
             catch (RegexError& err)
             {
                 if (event == PromptEvent::Validate)
-                    throw runtime_error("regex error: "_str + err.what());
+                    throw runtime_error(format("regex error: {}", err.what()));
                 else
                     context.input_handler().set_prompt_face(get_face("Error"));
             }
             catch (std::runtime_error& err)
             {
                 if (event == PromptEvent::Validate)
-                    throw runtime_error("regex error: "_str + err.what());
+                    throw runtime_error(format("regex error: {}", err.what()));
                 else
                 {
                     context.input_handler().set_prompt_face(get_face("Error"));
@@ -643,7 +643,7 @@ void search_next(Context& context, NormalParams params)
         }
         catch (RegexError& err)
         {
-            throw runtime_error("regex error: "_str + err.what());
+            throw runtime_error(format("regex error: ", err.what()));
         }
     }
     else
diff --git a/src/option_types.hh b/src/option_types.hh
index a8fd7d78..265d3c23 100644
--- a/src/option_types.hh
+++ b/src/option_types.hh
@@ -178,7 +178,7 @@ inline void option_from_string(StringView str, LineAndColumn<EffectiveType, Line
 {
     auto vals = split(str, tuple_separator);
     if (vals.size() != 2)
-        throw runtime_error("expected <line>"_str + tuple_separator + "<column>");
+        throw runtime_error(format("expected <line>{}<column>", tuple_separator));
     opt.line = str_to_int(vals[0]);
     opt.column = str_to_int(vals[1]);
 }
diff --git a/src/regex.cc b/src/regex.cc
index 4df06dc6..d678a62a 100644
--- a/src/regex.cc
+++ b/src/regex.cc
@@ -19,7 +19,7 @@ void option_from_string(StringView str, Regex& re)
     }
     catch (RegexError& err)
     {
-        throw runtime_error("unable to create regex: "_str + err.what());
+        throw runtime_error(format("unable to create regex: {}", err.what()));
     }
 }
 
diff --git a/src/remote.cc b/src/remote.cc
index 94cdd6c4..05da041c 100644
--- a/src/remote.cc
+++ b/src/remote.cc
@@ -624,10 +624,10 @@ Server::Server(String session_name)
     sockaddr_un addr = session_addr(m_session);
 
     if (bind(listen_sock, (sockaddr*) &addr, sizeof(sockaddr_un)) == -1)
-       throw runtime_error("unable to bind listen socket "_str + addr.sun_path);
+       throw runtime_error(format("unable to bind listen socket '{}'", addr.sun_path));
 
     if (listen(listen_sock, 4) == -1)
-       throw runtime_error("unable to listen on socket "_str + addr.sun_path);
+       throw runtime_error(format("unable to listen on socket '{}'", addr.sun_path));
 
     auto accepter = [this](FDWatcher& watcher, EventMode mode) {
         sockaddr_un client_addr;
diff --git a/src/shell_manager.cc b/src/shell_manager.cc
index 15453296..a7dae6cb 100644
--- a/src/shell_manager.cc
+++ b/src/shell_manager.cc
@@ -18,11 +18,7 @@ static const Regex env_var_regex(R"(\bkak_(\w+)\b)");
 ShellManager::ShellManager()
 {
     const char* path = getenv("PATH");
-    String new_path;
-    if (path)
-        new_path = path + ":"_str;
-
-    new_path += split_path(get_kak_binary_path()).first;
+    auto new_path = format("{}:{}", path, split_path(get_kak_binary_path()).first);
     setenv("PATH", new_path.c_str(), 1);
 }
 
@@ -98,7 +94,7 @@ std::pair<String, int> ShellManager::eval(
             else try
             {
                 String value = get_val(name, context);
-                setenv(("kak_"_str + name).c_str(), value.c_str(), 1);
+                setenv(format("kak_{}", name).c_str(), value.c_str(), 1);
             }
             catch (runtime_error&) {}
         }
diff --git a/src/string.hh b/src/string.hh
index 2108c64e..5d3855f1 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -132,7 +132,7 @@ public:
     constexpr StringView() = default;
     constexpr StringView(const char* data, ByteCount length)
         : m_data{data}, m_length{length} {}
-    constexpr StringView(const char* data) : m_data{data}, m_length{strlen(data)} {}
+    constexpr StringView(const char* data) : m_data{data}, m_length{data ? strlen(data) : 0} {}
     constexpr StringView(const char* begin, const char* end) : m_data{begin}, m_length{(int)(end - begin)} {}
     StringView(const String& str) : m_data{str.data()}, m_length{(int)str.length()} {}
     StringView(const char& c) : m_data(&c), m_length(1) {}