diff --git a/pam_yubico.c b/pam_yubico.c
index c36ca0e..cb50bfc 100644
--- a/pam_yubico.c
+++ b/pam_yubico.c
@@ -819,7 +819,7 @@ parse_cfg (int flags, int argc, const char **argv, struct cfg *cfg)
                 {
                   if(S_ISREG(st.st_mode))
                     {
-                      file = fopen(filename, "a");
+                      file = fopen(filename, "ae");
                       if(file)
                         {
                           cfg->debug_file = file;
diff --git a/util.c b/util.c
index 2112a58..d2cfc8d 100644
--- a/util.c
+++ b/util.c
@@ -188,7 +188,7 @@ int generate_random(void *buf, int len)
 	FILE *u;
 	int res;
 
-	u = fopen("/dev/urandom", "r");
+	u = fopen("/dev/urandom", "re");
 	if (!u) {
 		return -1;
 	}
diff --git a/ykpamcfg.c b/ykpamcfg.c
index 16dbb86..cfc4cd0 100644
--- a/ykpamcfg.c
+++ b/ykpamcfg.c
@@ -237,7 +237,7 @@ do_add_hmac_chalresp(YK_KEY *yk, uint8_t slot, bool verbose, char *output_dir, u
 
   umask(077);
 
-  f = fopen (fn, "w");
+  f = fopen (fn, "we");
   if (! f) {
     fprintf (stderr, "Failed opening '%s' for writing : %s\n", fn, strerror (errno));
     goto out;