diff --git a/include/spdlog/common-inl.h b/include/spdlog/common-inl.h
index be0d8f8e..9c967248 100644
--- a/include/spdlog/common-inl.h
+++ b/include/spdlog/common-inl.h
@@ -9,11 +9,15 @@
 
 namespace spdlog {
 namespace level {
+
+#if __cplusplus >= 201402L
+constexpr
+#endif
 static string_view_t level_string_views[] SPDLOG_LEVEL_NAMES;
 
 static const char *short_level_names[] SPDLOG_SHORT_LEVEL_NAMES;
 
-SPDLOG_INLINE string_view_t &to_string_view(spdlog::level::level_enum l) SPDLOG_NOEXCEPT
+SPDLOG_INLINE const string_view_t &to_string_view(spdlog::level::level_enum l) SPDLOG_NOEXCEPT
 {
     return level_string_views[l];
 }
diff --git a/include/spdlog/common.h b/include/spdlog/common.h
index 35342317..2ba355c7 100644
--- a/include/spdlog/common.h
+++ b/include/spdlog/common.h
@@ -166,7 +166,7 @@ enum level_enum
     }
 #endif
 
-SPDLOG_API string_view_t &to_string_view(spdlog::level::level_enum l) SPDLOG_NOEXCEPT;
+SPDLOG_API const string_view_t &to_string_view(spdlog::level::level_enum l) SPDLOG_NOEXCEPT;
 SPDLOG_API const char *to_short_c_str(spdlog::level::level_enum l) SPDLOG_NOEXCEPT;
 SPDLOG_API spdlog::level::level_enum from_str(const std::string &name) SPDLOG_NOEXCEPT;
 
diff --git a/include/spdlog/pattern_formatter-inl.h b/include/spdlog/pattern_formatter-inl.h
index 1408bb5c..54346e1e 100644
--- a/include/spdlog/pattern_formatter-inl.h
+++ b/include/spdlog/pattern_formatter-inl.h
@@ -129,7 +129,7 @@ public:
 
     void format(const details::log_msg &msg, const std::tm &, memory_buf_t &dest) override
     {
-        string_view_t &level_name = level::to_string_view(msg.level);
+        const string_view_t &level_name = level::to_string_view(msg.level);
         ScopedPadder p(level_name.size(), padinfo_, dest);
         fmt_helper::append_string_view(level_name, dest);
     }