diff --git a/src/config.c b/src/config.c
index 2e2000e..00e1aed 100644
--- a/src/config.c
+++ b/src/config.c
@@ -47,14 +47,25 @@ bad:
 	dp_log_fatal("Config: invalid color %s on line %d", value, line_idx);
 }
 
-static void load_int(const char *value, int line_idx, int *out) {
-	// Only nonnegative numbers
+static void load_int(const char *value, int line_idx, int min, int max, int *out) {
+	const char *p = value;
+	int mul = 1;
+	if (*p == '-') {
+		++p;
+		mul = -1;
+	}
+
 	*out = 0;
-	for (size_t i = 0; value[i] != '\0'; i++) {
-		if ((value[i] < '0' && value[i] > 9) || *out > INT_MAX / 10) {
+	for (; *p != '\0'; p++) {
+		if ((*p < '0' && *p > 9) || *out >= INT_MAX / 10) {
 			dp_log_fatal("Config: invalid number %s on line %d", value, line_idx);
 		}
-		*out = *out * 10 - '0' + value[i];
+		*out = *out * 10 - '0' + *p;
+	}
+	*out *= mul;
+
+	if (*out < min || *out > max) {
+		dp_log_fatal("Config: number %s on line %d is out of range", value, line_idx);
 	}
 }
 
@@ -174,13 +185,9 @@ void dp_config_load(struct dp_config *config, const char *user_path) {
 		} else if (strcmp(key, "border-color") == 0) {
 			load_color(value, line_idx, config->border_color);
 		} else if (strcmp(key, "border-size") == 0) {
-			load_int(value, line_idx, &config->border_size);
+			load_int(value, line_idx, 0, INT_MAX, &config->border_size);
 		} else if (strcmp(key, "png-compression") == 0) {
-			load_int(value, line_idx, &config->png_compression);
-			if (config->png_compression > 9) {
-				dp_log_fatal(
-						"Config: invalid value %d for png-compression", config->png_compression);
-			}
+			load_int(value, line_idx, 0, 9, &config->png_compression);
 		} else if (strcmp(key, "quick-select") == 0) {
 			load_bool(value, line_idx, &config->quick_select);
 		} else if (strcmp(key, "quit-key") == 0) {