diff --git a/src/ui.zig b/src/ui.zig
index c2cfb5c..8401910 100644
--- a/src/ui.zig
+++ b/src/ui.zig
@@ -12,7 +12,7 @@ pub const c = @cImport({
     @cInclude("string.h");
     @cInclude("curses.h");
     @cInclude("time.h");
-    @cDefine("_X_OPEN_SOURCE", "1");
+    @cDefine("_XOPEN_SOURCE", "1");
     @cInclude("wchar.h");
     @cInclude("locale.h");
 });