diff --git a/pkgs/c/compat.glfw.lua b/pkgs/c/compat.glfw.lua
index a4462886..c7014221 100644
--- a/pkgs/c/compat.glfw.lua
+++ b/pkgs/c/compat.glfw.lua
@@ -155,6 +155,16 @@ package = {
             },
         },
         windows = {
+            -- THE WIN32 BACKEND IS WRITTEN FOR THE SYSTEM'S C LIBRARY AND ITS
+            -- HEADERS (<windows.h>, user32, gdi32): a requirement on the target
+            -- side (mcpp SPEC-002 §2.2), as the Linux row states glibc. Every
+            -- route that has the Win32 API answers it -- the MSVC row, the
+            -- MinGW-w64 payload and the mingw-w64-sysroot base, which mcpp's
+            -- mingw-llvm provider supplies on every host (macOS and Linux
+            -- included). A Windows identity whose C library is another
+            -- (openkal-musl over openkal-windows) has no window system, and is
+            -- refused at resolution, naming this requirement.
+            requires = { "mcpp:c-abi=ucrt" },
             cflags = { "-D_GLFW_WIN32", "-DUNICODE", "-D_UNICODE" },
             sources = {
                 "src/win32_time.c",