diff --git a/ChangeLog b/ChangeLog
index 87c259b..dde5030 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2024-11-10  Dirk Eddelbuettel  <edd@debian.org>
+
+	* src/formatter.cpp: Partially revert / simplify previous PR
+
+2024-11-09  Dirk Eddelbuettel  <edd@debian.org>
+
+	* inst/include/spdlog/*: New upstream release spdlog 1.15.0
+
 2024-10-29  Dirk Eddelbuettel  <edd@debian.org>
 
 	* DESCRIPTION (Version, Date): Roll micro release version
diff --git a/src/formatter.cpp b/src/formatter.cpp
index ab71ac0..d2e4c4b 100644
--- a/src/formatter.cpp
+++ b/src/formatter.cpp
@@ -3,21 +3,21 @@
 
 #include <RcppSpdlog>
 
+// we accommodate C++20 where fmt::format is available as std::format
+// this defines a helper function used below
 #if defined(SPDLOG_USE_STD_FORMAT) && __cplusplus >= 202002L
-#define NAMESPACE std
-#else
-#define NAMESPACE fmt
-#endif
 
-template<std::size_t... S>
-NAMESPACE::format_args unpack_vector(const std::vector<std::string>& vec, std::index_sequence<S...>) {
-    return NAMESPACE::make_format_args(vec[S]...);
-}
+    template<std::size_t... S>
+    std::format_args unpack_vector(const std::vector<std::string>& vec, std::index_sequence<S...>) {
+        return std::make_format_args(vec[S]...);
+    }
 
-template<std::size_t size>
-NAMESPACE::format_args unpack_vector(const std::vector<std::string>& vec) {
-    return unpack_vector(vec, std::make_index_sequence<size>());
-}
+    template<std::size_t size>
+    std::format_args unpack_vector(const std::vector<std::string>& vec) {
+        return unpack_vector(vec, std::make_index_sequence<size>());
+    }
+
+#endif
 
 //' Simple Pass-Through Formatter to \code{fmt::format()}
 //'
@@ -39,26 +39,48 @@ NAMESPACE::format_args unpack_vector(const std::vector<std::string>& vec) {
 std::string formatter(const std::string s, std::vector<std::string> v) {
     size_t n = v.size();
     switch (n) {
-        case 0: return NAMESPACE::vformat(NAMESPACE::string_view(s), NAMESPACE::make_format_args());
-        case 1: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<1>(v));
-        case 2: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<2>(v));
-        case 3: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<3>(v));
-        case 4: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<4>(v));
-        case 5: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<5>(v));
-        case 6: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<6>(v));
-        case 7: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<7>(v));
-        case 8: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<8>(v));
-        case 9: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<9>(v));
-        case 10: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<10>(v));
-        case 11: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<11>(v));
-        case 12: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<12>(v));
-        case 13: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<13>(v));
-        case 14: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<14>(v));
-        case 15: return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<15>(v));
+#if defined(SPDLOG_USE_STD_FORMAT) && __cplusplus >= 202002L
+        case 0: return std::vformat(std::string_view(s), std::make_format_args());
+        case 1: return std::vformat(std::string_view(s), unpack_vector<1>(v));
+        case 2: return std::vformat(std::string_view(s), unpack_vector<2>(v));
+        case 3: return std::vformat(std::string_view(s), unpack_vector<3>(v));
+        case 4: return std::vformat(std::string_view(s), unpack_vector<4>(v));
+        case 5: return std::vformat(std::string_view(s), unpack_vector<5>(v));
+        case 6: return std::vformat(std::string_view(s), unpack_vector<6>(v));
+        case 7: return std::vformat(std::string_view(s), unpack_vector<7>(v));
+        case 8: return std::vformat(std::string_view(s), unpack_vector<8>(v));
+        case 9: return std::vformat(std::string_view(s), unpack_vector<9>(v));
+        case 10: return std::vformat(std::string_view(s), unpack_vector<10>(v));
+        case 11: return std::vformat(std::string_view(s), unpack_vector<11>(v));
+        case 12: return std::vformat(std::string_view(s), unpack_vector<12>(v));
+        case 13: return std::vformat(std::string_view(s), unpack_vector<13>(v));
+        case 14: return std::vformat(std::string_view(s), unpack_vector<14>(v));
+        case 15: return std::vformat(std::string_view(s), unpack_vector<15>(v));
         default: {
             Rcpp::warning("Only up to fifteen arguments support for now.");
-            return NAMESPACE::vformat(NAMESPACE::string_view(s), unpack_vector<12>(v));
+            return std::vformat(std::string_view(s), unpack_vector<12>(v));
         }
+#else
+        case 0: return fmt::format(s);
+        case 1: return fmt::format(s, std::string(v[0]));
+        case 2: return fmt::format(s, std::string(v[0]), std::string(v[1]));
+        case 3: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]));
+        case 4: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]));
+        case 5: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]));
+        case 6: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]));
+        case 7: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]));
+        case 8: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]));
+        case 9: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]));
+        case 10: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]));
+        case 11: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]), std::string(v[10]));
+        case 12: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]), std::string(v[10]), std::string(v[11]));
+        case 13: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]), std::string(v[10]), std::string(v[11]), std::string(v[12]));
+        case 14: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]), std::string(v[10]), std::string(v[11]), std::string(v[12]), std::string(v[13]));
+        case 15: return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]), std::string(v[10]), std::string(v[11]), std::string(v[12]), std::string(v[13]), std::string(v[14]));
+        default: {
+            Rcpp::warning("Only up to fifteen arguments support for now.");
+            return fmt::format(s, std::string(v[0]), std::string(v[1]), std::string(v[2]), std::string(v[3]), std::string(v[4]), std::string(v[5]), std::string(v[6]), std::string(v[7]), std::string(v[8]), std::string(v[9]), std::string(v[10]), std::string(v[11]));
+        }
+#endif
     }
 }
-