diff --git a/ds4_agent.c b/ds4_agent.c
index c16d6499..95f92925 100644
--- a/ds4_agent.c
+++ b/ds4_agent.c
@@ -388,11 +388,16 @@ static bool parse_power_percent(const char *arg, int *out) {
     return true;
 }
 
-static uint64_t parse_u64(const char *s, const char *opt) {
+static uint64_t parse_seed(const char *s) {
     char *end = NULL;
+    if (s[0] == '\0' || s[0] == '-') {
+        fprintf(stderr, "ds4-agent: invalid value for --seed: %s\n", s);
+        exit(2);
+    }
+    errno = 0;
     unsigned long long v = strtoull(s, &end, 10);
-    if (s[0] == '\0' || *end != '\0' || v == 0) {
-        fprintf(stderr, "ds4-agent: invalid value for %s: %s\n", opt, s);
+    if (*end != '\0' || errno == ERANGE || v == 0) {
+        fprintf(stderr, "ds4-agent: invalid value for --seed: %s\n", s);
         exit(2);
     }
     return (uint64_t)v;
@@ -541,7 +546,7 @@ static agent_config parse_options(int argc, char **argv) {
         } else if (!strcmp(arg, "--min-p")) {
             c.gen.min_p = parse_float_range(need_arg(&i, argc, argv, arg), arg, 0.0f, 1.0f);
         } else if (!strcmp(arg, "--seed")) {
-            c.gen.seed = parse_u64(need_arg(&i, argc, argv, arg), arg);
+            c.gen.seed = parse_seed(need_arg(&i, argc, argv, arg));
         } else if (!strcmp(arg, "--think")) {
             c.gen.think_mode = DS4_THINK_HIGH;
         } else if (!strcmp(arg, "--think-max")) {
diff --git a/ds4_cli.c b/ds4_cli.c
index 7bd1bb37..e01de61a 100644
--- a/ds4_cli.c
+++ b/ds4_cli.c
@@ -214,11 +214,16 @@ static int parse_int(const char *s, const char *opt) {
     return (int)v;
 }
 
-static uint64_t parse_u64(const char *s, const char *opt) {
+static uint64_t parse_seed(const char *s) {
     char *end = NULL;
+    if (s[0] == '\0' || s[0] == '-') {
+        fprintf(stderr, "ds4: invalid value for --seed: %s\n", s);
+        exit(2);
+    }
+    errno = 0;
     unsigned long long v = strtoull(s, &end, 10);
-    if (s[0] == '\0' || *end != '\0' || v == 0) {
-        fprintf(stderr, "ds4: invalid value for %s: %s\n", opt, s);
+    if (*end != '\0' || errno == ERANGE || v == 0) {
+        fprintf(stderr, "ds4: invalid value for --seed: %s\n", s);
         exit(2);
     }
     return (uint64_t)v;
@@ -1444,7 +1449,7 @@ static cli_config parse_options(int argc, char **argv) {
         } else if (!strcmp(arg, "--min-p")) {
             c.gen.min_p = parse_float_range(need_arg(&i, argc, argv, arg), arg, 0.0f, 1.0f);
         } else if (!strcmp(arg, "--seed")) {
-            c.gen.seed = parse_u64(need_arg(&i, argc, argv, arg), arg);
+            c.gen.seed = parse_seed(need_arg(&i, argc, argv, arg));
         } else if (!strcmp(arg, "--quality")) {
             c.engine.quality = true;
         } else if (!strcmp(arg, "--power")) {
diff --git a/ds4_eval.c b/ds4_eval.c
index 5d80e88c..ccf0f92b 100644
--- a/ds4_eval.c
+++ b/ds4_eval.c
@@ -1429,11 +1429,16 @@ static int parse_int_arg(const char *s, const char *opt) {
     return (int)v;
 }
 
-static uint64_t parse_u64_arg(const char *s, const char *opt) {
+static uint64_t parse_seed_arg(const char *s) {
     char *end = NULL;
+    if (s[0] == '\0' || s[0] == '-') {
+        fprintf(stderr, "ds4-eval: invalid value for --seed: %s\n", s);
+        exit(2);
+    }
+    errno = 0;
     unsigned long long v = strtoull(s, &end, 10);
-    if (s[0] == '\0' || *end != '\0' || v == 0) {
-        fprintf(stderr, "ds4-eval: invalid value for %s: %s\n", opt, s);
+    if (*end != '\0' || errno == ERANGE || v == 0) {
+        fprintf(stderr, "ds4-eval: invalid value for --seed: %s\n", s);
         exit(2);
     }
     return (uint64_t)v;
@@ -1556,7 +1561,7 @@ static eval_config parse_options(int argc, char **argv) {
         } else if (!strcmp(arg, "--min-p")) {
             c.min_p = parse_float_arg(need_arg(&i, argc, argv, arg), arg, 0.0f, 1.0f);
         } else if (!strcmp(arg, "--seed")) {
-            c.seed = parse_u64_arg(need_arg(&i, argc, argv, arg), arg);
+            c.seed = parse_seed_arg(need_arg(&i, argc, argv, arg));
         } else if (!strcmp(arg, "--trace")) {
             c.trace_path = need_arg(&i, argc, argv, arg);
         } else if (!strcmp(arg, "--regrade-trace")) {
diff --git a/ds4_server.c b/ds4_server.c
index 62fabc1b..73b3ad5e 100644
--- a/ds4_server.c
+++ b/ds4_server.c
@@ -11235,6 +11235,17 @@ static int parse_nonneg_int_arg(const char *s, const char *opt) {
     return (int)v;
 }
 
+static int parse_port_arg(const char *s) {
+    char *end = NULL;
+    errno = 0;
+    long v = strtol(s, &end, 10);
+    if (!s[0] || *end || errno == ERANGE || v < 1 || v > 65535) {
+        server_log(DS4_LOG_DEFAULT, "ds4-server: --port must be between 1 and 65535: %s", s);
+        exit(2);
+    }
+    return (int)v;
+}
+
 static float parse_float_arg(const char *s, const char *opt, float minv, float maxv) {
     char *end = NULL;
     float v = strtof(s, &end);
@@ -11439,7 +11450,7 @@ static server_config parse_options(int argc, char **argv) {
         } else if (!strcmp(arg, "--host")) {
             c.host = need_arg(&i, argc, argv, arg);
         } else if (!strcmp(arg, "--port")) {
-            c.port = parse_int_arg(need_arg(&i, argc, argv, arg), arg);
+            c.port = parse_port_arg(need_arg(&i, argc, argv, arg));
         } else if (!strcmp(arg, "--cors")) {
             c.enable_cors = true;
         } else if (!strcmp(arg, "--trace")) {