diff --git a/include/blt/compatibility.h b/include/blt/compatibility.h
index cfe0e85..c49e4ea 100644
--- a/include/blt/compatibility.h
+++ b/include/blt/compatibility.h
@@ -21,9 +21,11 @@
 
 #if __cplusplus >= 202002L
     #define BLT_CONTAINS(container, value) container.contains(value)
+    #define BLT_CPP20_CONSTEXPR constexpr
 #else
     #include <algorithm>
     #define BLT_CONTAINS(container, value) std::find(container.begin(), container.end(), value) != container.end()
+    #define BLT_CPP20_CONSTEXPR
 #endif
 
 #define INCLUDE_FS \
diff --git a/include/blt/std/string.h b/include/blt/std/string.h
index 97179ce..9581328 100755
--- a/include/blt/std/string.h
+++ b/include/blt/std/string.h
@@ -13,12 +13,7 @@
 #include <algorithm>
 #include <vector>
 #include <cctype>
-
-#if __cplusplus >= 202002L
-    #define BLT_CPP20_CONSTEXPR constexpr
-#else
-    #define BLT_CPP20_CONSTEXPR
-#endif
+#include <blt/compatibility.h>
 
 namespace blt::string
 {