diff --git a/src/command_manager.cc b/src/command_manager.cc
index 2255b7c45..c8e5d05aa 100644
--- a/src/command_manager.cc
+++ b/src/command_manager.cc
@@ -31,9 +31,11 @@ void CommandManager::register_commands(memoryview<String> command_names,
         m_commands[command_name] = { command, completer };
 }
 
-parse_error::parse_error(const String& error)
-    : runtime_error{"parse error: " + error} {}
-
+struct parse_error : runtime_error
+{
+    parse_error(const String& error)
+        : runtime_error{"parse error: " + error} {}
+};
 
 namespace
 {
diff --git a/src/command_manager.hh b/src/command_manager.hh
index c63633ef9..9aee1e0c2 100644
--- a/src/command_manager.hh
+++ b/src/command_manager.hh
@@ -14,15 +14,9 @@
 namespace Kakoune
 {
 
-struct parse_error : runtime_error
-{
-    parse_error(const String& error);
-};
-
 struct Context;
 using CommandParameters = memoryview<String>;
-using Command = std::function<void (CommandParameters,
-                                    Context& context)>;
+using Command = std::function<void (CommandParameters, Context& context)>;
 using CommandCompleter = std::function<CandidateList (const Context& context,
                                                       CommandParameters,
                                                       size_t, ByteCount)>;
diff --git a/src/main.cc b/src/main.cc
index ad41d8434..536ca1577 100644
--- a/src/main.cc
+++ b/src/main.cc
@@ -43,7 +43,7 @@ String runtime_directory()
 #elif defined(__APPLE__)
     uint32_t bufsize = 2048;
     _NSGetExecutablePath(buffer, &bufsize);
-    char* canonical_path = realpath(buffer, NULL);
+    char* canonical_path = realpath(buffer, nullptr);
     strncpy(buffer, canonical_path, 2048);
     free(canonical_path);
 #else
diff --git a/src/remote.cc b/src/remote.cc
index 5776d6241..6bb267505 100644
--- a/src/remote.cc
+++ b/src/remote.cc
@@ -327,7 +327,7 @@ bool RemoteUI::is_key_available()
 
     tv.tv_sec = 0;
     tv.tv_usec = 0;
-    int res = select(sock+1, &rfds, NULL, NULL, &tv);
+    int res = select(sock+1, &rfds, nullptr, nullptr, &tv);
     return res == 1;
 }
 
@@ -500,7 +500,7 @@ private:
             FD_ZERO(&rfds);
             FD_SET(socket, &rfds);
         }
-        while (select(socket+1, &rfds, NULL, NULL, &tv) == 1);
+        while (select(socket+1, &rfds, nullptr, nullptr, &tv) == 1);
     }
 
     String    m_buffer;
diff --git a/src/shell_manager.cc b/src/shell_manager.cc
index d293a1377..7663e2f85 100644
--- a/src/shell_manager.cc
+++ b/src/shell_manager.cc
@@ -67,7 +67,7 @@ String ShellManager::pipe(const String& input,
         if (not errorout.empty())
             write_debug("shell stderr: <<<\n" + errorout + ">>>");
 
-        waitpid(pid, NULL, 0);
+        waitpid(pid, nullptr, 0);
     }
     else try
     {
@@ -125,7 +125,7 @@ String ShellManager::pipe(const String& input,
             execparams.push_back(shell.c_str());
         for (auto& param : params)
             execparams.push_back(param.c_str());
-        execparams.push_back(NULL);
+        execparams.push_back(nullptr);
 
         execvp(shell.c_str(), (char* const*)execparams.data());
         exit(-1);