diff --git a/libc/bionic/strchr.cpp b/libc/bionic/strchr.cpp
index e2f447169..029fbd9d7 100644
--- a/libc/bionic/strchr.cpp
+++ b/libc/bionic/strchr.cpp
@@ -27,6 +27,7 @@
  * SUCH DAMAGE.
  */
 
+#undef _FORTIFY_SOURCE
 #include <string.h>
 
 extern "C" char* strchr(const char* p, int ch) {
diff --git a/libc/stdio/snprintf.c b/libc/stdio/snprintf.c
index 5aa54be43..9a25ef2cd 100644
--- a/libc/stdio/snprintf.c
+++ b/libc/stdio/snprintf.c
@@ -31,6 +31,7 @@
  * SUCH DAMAGE.
  */
 
+#undef _FORTIFY_SOURCE
 #include <limits.h>
 #include <stdio.h>
 #include <string.h>
diff --git a/libc/stdio/sprintf.c b/libc/stdio/sprintf.c
index 3cf795224..124555277 100644
--- a/libc/stdio/sprintf.c
+++ b/libc/stdio/sprintf.c
@@ -31,6 +31,7 @@
  * SUCH DAMAGE.
  */
 
+#undef _FORTIFY_SOURCE
 #include <stdio.h>
 #include <string.h>
 #include <stdarg.h>