diff --git a/color_math.c b/color_math.c
index ace8b17..59993a8 100644
--- a/color_math.c
+++ b/color_math.c
@@ -1,3 +1,5 @@
+#define _USE_MATH_DEFINES
+#define _XOPEN_SOURCE 700
 #define _POSIX_C_SOURCE 200809L
 #include <math.h>
 #include <errno.h>
diff --git a/main.c b/main.c
index 52f8239..2fe07db 100644
--- a/main.c
+++ b/main.c
@@ -1,3 +1,5 @@
+#define _DEFAULT_SOURCE
+#define _XOPEN_SOURCE 700
 #include <assert.h>
 #include <errno.h>
 #include <fcntl.h>
diff --git a/meson.build b/meson.build
index 0b13e4e..891a1a3 100644
--- a/meson.build
+++ b/meson.build
@@ -26,8 +26,6 @@ add_project_arguments(
 		'-Wno-unused-command-line-argument',
 		'-Wvla',
 		'-Wl,--exclude-libs=ALL',
-		'-D_USE_MATH_DEFINES',
-		'-D_XOPEN_SOURCE=700',
 		'-DWLSUNSET_VERSION="@0@"'.format(meson.project_version()),
 	],
 	language: 'c',
diff --git a/str_vec.c b/str_vec.c
index eb87b51..558b8be 100644
--- a/str_vec.c
+++ b/str_vec.c
@@ -1,3 +1,4 @@
+#define _XOPEN_SOURCE 700
 #include <stdlib.h>
 #include <string.h>