diff --git a/src/client_manager.cc b/src/client_manager.cc
index ad9a5009..6d4ef641 100644
--- a/src/client_manager.cc
+++ b/src/client_manager.cc
@@ -174,7 +174,8 @@ void ClientManager::clear_client_trash()
 
 bool ClientManager::validate_client_name(StringView name) const
 {
-    return const_cast<ClientManager*>(this)->get_client_ifp(name) == nullptr;
+    return all_of(name, is_identifier) and
+        const_cast<ClientManager*>(this)->get_client_ifp(name) == nullptr;
 }
 
 Client* ClientManager::get_client_ifp(StringView name)
diff --git a/src/commands.cc b/src/commands.cc
index eff21355..889a5307 100644
--- a/src/commands.cc
+++ b/src/commands.cc
@@ -846,7 +846,7 @@ void define_command(const ParametersParser& parser, Context& context, const Shel
     const String& cmd_name = parser[0];
     auto& cm = CommandManager::instance();
 
-    if (contains_that(cmd_name, is_blank))
+    if (not all_of(cmd_name, is_identifier))
         throw runtime_error(format("invalid command name: '{}'", cmd_name));
 
     if (cm.command_defined(cmd_name) and not parser.get_switch("allow-override"))
diff --git a/src/keymap_manager.cc b/src/keymap_manager.cc
index fd83757c..844f150f 100644
--- a/src/keymap_manager.cc
+++ b/src/keymap_manager.cc
@@ -61,7 +61,7 @@ void KeymapManager::add_user_mode(String user_mode_name)
     if (contains(user_modes(), user_mode_name))
         throw runtime_error(format("user mode '{}' already defined", user_mode_name));
 
-    if (contains_that(user_mode_name, is_blank))
+    if (not all_of(user_mode_name, is_identifier))
         throw runtime_error(format("invalid mode name: '{}'", user_mode_name));
 
     user_modes().push_back(std::move(user_mode_name));
diff --git a/src/option_manager.hh b/src/option_manager.hh
index 674cf6da..84c1be98 100644
--- a/src/option_manager.hh
+++ b/src/option_manager.hh
@@ -214,13 +214,11 @@ public:
                            const T& value,
                            OptionFlags flags = OptionFlags::None)
     {
-        auto is_not_identifier = [](char c) {
-            return (c < 'a' or c > 'z') and
-                   (c < 'A' or c > 'Z') and
-                   (c < '0' or c > '9') and c != '_';
+        auto is_option_identifier = [](char c) {
+            return is_basic_alpha(c) or is_basic_digit(c) or c == '_';
         };
 
-        if (contains_that(name, is_not_identifier))
+        if (not all_of(name, is_option_identifier))
             throw runtime_error{format("name '{}' contains char out of [a-zA-Z0-9_]", name)};
 
         auto& opts = m_global_manager.m_options;
diff --git a/src/ranges.hh b/src/ranges.hh
index 58f14db4..a762dd2f 100644
--- a/src/ranges.hh
+++ b/src/ranges.hh
@@ -338,6 +338,20 @@ bool contains_that(Range&& range, T op)
     return find_if(range, op) != end(range);
 }
 
+template<typename Range, typename T>
+bool all_of(Range&& range, T op)
+{
+    using std::begin; using std::end;
+    return std::all_of(begin(range), end(range), op);
+}
+
+template<typename Range, typename T>
+bool any_of(Range&& range, T op)
+{
+    using std::begin; using std::end;
+    return std::any_of(begin(range), end(range), op);
+}
+
 template<typename Range, typename U>
 void unordered_erase(Range&& vec, U&& value)
 {
diff --git a/src/remote.cc b/src/remote.cc
index 521663f6..f3dd7d06 100644
--- a/src/remote.cc
+++ b/src/remote.cc
@@ -777,8 +777,8 @@ private:
 Server::Server(String session_name)
     : m_session{std::move(session_name)}
 {
-    if (contains(m_session, '/'))
-        throw runtime_error{"Cannot create sessions with '/' in their name"};
+    if (not all_of(m_session, is_identifier))
+        throw runtime_error{format("Invalid session name '{}'", session_name)};
 
     int listen_sock = socket(AF_UNIX, SOCK_STREAM, 0);
     fcntl(listen_sock, F_SETFD, FD_CLOEXEC);
@@ -816,8 +816,8 @@ Server::Server(String session_name)
 
 bool Server::rename_session(StringView name)
 {
-    if (contains(name, '/'))
-        throw runtime_error{"Cannot create sessions with '/' in their name"};
+    if (not all_of(name, is_identifier))
+        throw runtime_error{format("Invalid session name '{}'", name)};
 
     String old_socket_file = format("{}/kakoune/{}/{}", tmpdir(),
                                     get_user_name(geteuid()), m_session);
diff --git a/src/unicode.hh b/src/unicode.hh
index 01fcfb23..1dcc836b 100644
--- a/src/unicode.hh
+++ b/src/unicode.hh
@@ -53,6 +53,17 @@ inline bool is_basic_alpha(Codepoint c) noexcept
     return (c >= 'a' and c <= 'z') or (c >= 'A' and c <= 'Z');
 }
 
+inline bool is_basic_digit(Codepoint c) noexcept
+{
+    return c >= '0' and c <= '9';
+}
+
+inline bool is_identifier(Codepoint c) noexcept
+{
+    return is_basic_alpha(c) or is_basic_digit(c) or
+           c == '_' or c == '-';
+}
+
 inline ColumnCount codepoint_width(Codepoint c) noexcept
 {
     if (c == '\n')