diff --git a/include/sys/select.h b/include/sys/select.h
index df32003..29819be 100644
--- a/include/sys/select.h
+++ b/include/sys/select.h
@@ -49,12 +49,23 @@ _STI void __fortify_FD_SET(int __f, fd_set * _FORTIFY_POS0 __s)
 	FD_SET(__f, __s);
 }
 
+_STI int __fortify_FD_ISSET(int __f, fd_set * _FORTIFY_POS0 __s)
+{
+	size_t __b = __bos(__s, 0);
+
+	if (__f < 0 || __f >= FD_SETSIZE || __b < sizeof(fd_set))
+		__builtin_trap();
+	return FD_ISSET(__f, __s);
+}
+
 #undef _STI
 
 #undef FD_CLR
 #define FD_CLR(fd, set) __fortify_FD_CLR(fd, set)
 #undef FD_SET
 #define FD_SET(fd, set) __fortify_FD_SET(fd, set)
+#undef FD_ISSET
+#define FD_ISSET(fd, set) __fortify_FD_ISSET(fd, set)
 
 #ifdef __cplusplus
 }
diff --git a/tests/Makefile b/tests/Makefile
index 5f70069..a93e0e9 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -10,6 +10,8 @@ RUNTIME_TARGETS= \
 	test_FD_CLR_negative         \
 	test_FD_SET_SETSIZE          \
 	test_FD_SET_negative         \
+	test_FD_ISSET_SETSIZE        \
+	test_FD_ISSET_negative       \
 	test_bcopy_dynamic_read      \
 	test_bcopy_dynamic_write     \
 	test_bcopy_static_read       \
diff --git a/tests/test_FD_ISSET_SETSIZE.c b/tests/test_FD_ISSET_SETSIZE.c
new file mode 100644
index 0000000..0362aaa
--- /dev/null
+++ b/tests/test_FD_ISSET_SETSIZE.c
@@ -0,0 +1,14 @@
+#include "common.h"
+
+#include <sys/select.h>
+
+int main(int argc, char** argv) {
+  fd_set rfds;
+
+  CHK_FAIL_START
+  FD_ISSET(FD_SETSIZE, &rfds);
+  CHK_FAIL_END
+
+  puts((const char*)&rfds);
+  return ret;
+}
diff --git a/tests/test_FD_ISSET_negative.c b/tests/test_FD_ISSET_negative.c
new file mode 100644
index 0000000..f0ff89a
--- /dev/null
+++ b/tests/test_FD_ISSET_negative.c
@@ -0,0 +1,14 @@
+#include "common.h"
+
+#include <sys/select.h>
+
+int main(int argc, char** argv) {
+  fd_set rfds;
+
+  CHK_FAIL_START
+  FD_ISSET(-1, &rfds);
+  CHK_FAIL_END
+
+  puts((const char*)&rfds);
+  return ret;
+}