diff --git a/libvapours/include/vapours/defines.hpp b/libvapours/include/vapours/defines.hpp
index d76052c4..2c937e15 100644
--- a/libvapours/include/vapours/defines.hpp
+++ b/libvapours/include/vapours/defines.hpp
@@ -38,7 +38,7 @@
 #define WRAP_TEMPLATE_CONSTANT(...) ([] { using U = union { static constexpr auto GetValue() { return __VA_ARGS__; } }; return U{}; }())
 #define UNWRAP_TEMPLATE_CONSTANT(tpnm) (tpnm::GetValue())
 
-#define CONCATENATE_IMPL(S1, s2) s1##s2
+#define CONCATENATE_IMPL(s1, s2) s1##s2
 #define CONCATENATE(s1, s2) CONCATENATE_IMPL(s1, s2)
 
 #define BITSIZEOF(x) (sizeof(x) * CHAR_BIT)