diff --git a/ssh-agent.c b/ssh-agent.c
index e5232fc..f5fce6b 100644
--- a/ssh-agent.c
+++ b/ssh-agent.c
@@ -57,6 +57,10 @@
 #include "scard.h"
 #endif
 
+#if defined(HAVE_SYS_PRCTL_H)
+#include <sys/prctl.h>	/* For prctl() and PR_SET_DUMPABLE */
+#endif
+
 typedef enum {
 	AUTH_UNUSED,
 	AUTH_SOCKET,
@@ -1023,6 +1027,11 @@
 	setegid(getgid());
 	setgid(getgid());
 
+#if defined(HAVE_PRCTL) && defined(PR_SET_DUMPABLE)
+	/* Disable ptrace on Linux without sgid bit */
+	prctl(PR_SET_DUMPABLE, 0);
+#endif
+
 	SSLeay_add_all_algorithms();
 
 	__progname = ssh_get_progname(av[0]);