diff --git a/routes/css.cpp b/routes/css.cpp
index 57d1ec9..31b9958 100644
--- a/routes/css.cpp
+++ b/routes/css.cpp
@@ -134,7 +134,11 @@ static const constexpr char css[] = R"EOF(
 )EOF";
 #define CSS_LEN sizeof(css) / sizeof(css[0]) - 1
 
+#ifdef __cpp_consteval
 const uint64_t css_hash = FastHashConstEval(css, CSS_LEN, 0);
+#else
+const uint64_t css_hash = FastHash(css, CSS_LEN, 0);
+#endif
 
 void css_route(const httplib::Request& req, httplib::Response& res) {
     res.set_header("ETag", std::string(1, '"') + std::to_string(css_hash) + '"');
diff --git a/thirdparty/FastHash.h b/thirdparty/FastHash.h
index 9771eb7..f6b5815 100644
--- a/thirdparty/FastHash.h
+++ b/thirdparty/FastHash.h
@@ -39,6 +39,8 @@
 
 #pragma once
 
+#include <version>
+
 // Compression function for Merkle-Damgard construction.
 // This function is generated using the framework provided.
 //#define mix(h) ({
@@ -75,6 +77,8 @@ constexpr uint64_t FastHash(const char* str, size_t size, uint64_t seed/*, uint6
 	return mix(h);
 }
 
+#ifdef __cpp_consteval
 consteval uint64_t FastHashConstEval(const char* str, size_t size, uint64_t seed) {
     return FastHash(str, size, seed);
 }
+#endif