diff --git a/regressions/ck_backoff/validate/Makefile b/regressions/ck_backoff/validate/Makefile
index ac87155..60cd40b 100644
--- a/regressions/ck_backoff/validate/Makefile
+++ b/regressions/ck_backoff/validate/Makefile
@@ -12,3 +12,4 @@ clean:
 	rm -rf validate *.dSYM
 
 include ../../../build/regressions.build
+CFLAGS+=-D_GNU_SOURCE
diff --git a/regressions/common.h b/regressions/common.h
index 6f12bd4..b8a158d 100644
--- a/regressions/common.h
+++ b/regressions/common.h
@@ -28,7 +28,6 @@
 #include <ck_pr.h>
 
 #ifdef __linux__
-#define _GNU_SOURCE
 #include <sched.h>
 #include <unistd.h>
 #include <sys/types.h>