diff --git a/src/cron/c/parse.c b/src/cron/c/parse.c
index c536237..1ac23c0 100644
--- a/src/cron/c/parse.c
+++ b/src/cron/c/parse.c
@@ -67,9 +67,14 @@ cron_parse_error ce_parse_range(uint64_t *out, char *s, uint8_t min, uint8_t max
 	uint8_t end = max;
 	uint8_t interval = 0;
 
-	if (s[0] == '*' && strlen(s) == 1) {
-		start = min;
-		interval = 1;
+	if (s[0] == '*') {
+		// A star character is only allowed on its own
+		if (s[1] == '\0' && dash_index == 0) {
+			start = min;
+			interval = 1;
+		} else {
+			return cron_parse_invalid_expression;
+		}
 	}else {
 		SAFE_ATOI(start, s, min, max);
 
diff --git a/src/cron/expression.c.v b/src/cron/expression.c.v
index cd4b8b0..0217ca3 100644
--- a/src/cron/expression.c.v
+++ b/src/cron/expression.c.v
@@ -18,6 +18,45 @@ pub struct C.cron_expression {
 
 pub type Expression = C.cron_expression
 
+// == returns whether the two expressions are equal by value.
+fn (ce1 Expression) == (ce2 Expression) bool {
+	if ce1.month_count != ce2.month_count || ce1.day_count != ce2.day_count
+		|| ce1.hour_count != ce2.hour_count || ce1.minute_count != ce2.minute_count {
+		return false
+	}
+
+	for i in 0 .. ce1.month_count {
+		unsafe {
+			if ce1.months[i] != ce2.months[i] {
+				return false
+			}
+		}
+	}
+	for i in 0 .. ce1.day_count {
+		unsafe {
+			if ce1.days[i] != ce2.days[i] {
+				return false
+			}
+		}
+	}
+	for i in 0 .. ce1.hour_count {
+		unsafe {
+			if ce1.hours[i] != ce2.hours[i] {
+				return false
+			}
+		}
+	}
+	for i in 0 .. ce1.minute_count {
+		unsafe {
+			if ce1.minutes[i] != ce2.minutes[i] {
+				return false
+			}
+		}
+	}
+
+	return true
+}
+
 struct C.cron_simple_time {
 	year   int
 	month  int
diff --git a/src/cron/expression_test.v b/src/cron/expression_test.v
index 4023012..a8ec5a5 100644
--- a/src/cron/expression_test.v
+++ b/src/cron/expression_test.v
@@ -34,13 +34,3 @@ fn test_next_simple() ! {
 	//// Overlap to next year
 	util_test_time('0 3', '2002-12-31 04:00:00', '2003-01-01 03:00:00')!
 }
-
-fn test_leading_star() {
-	mut x := false
-	parse_expression('*5 8') or { x = true }
-	assert x
-
-	x = false
-	parse_expression('x 8') or { x = true }
-	assert x
-}
diff --git a/src/cron/parse_test.v b/src/cron/parse_test.v
new file mode 100644
index 0000000..692a381
--- /dev/null
+++ b/src/cron/parse_test.v
@@ -0,0 +1,37 @@
+module cron
+
+fn test_not_allowed() {
+	mut res := false
+	parse_expression('4 *-7') or { res = true }
+	assert res
+
+	res = false
+	parse_expression('4 *-7/4') or { res = true }
+	assert res
+
+	res = false
+	parse_expression('4 7/*') or { res = true }
+	assert res
+
+	res = false
+	parse_expression('0 0 30 2') or { res = true }
+	assert res
+}
+
+fn test_leading_star() {
+	mut x := false
+	parse_expression('*5 8') or { x = true }
+	assert x
+
+	x = false
+	parse_expression('x 8') or { x = true }
+	assert x
+}
+
+fn test_auto_extend() ! {
+	ce1 := parse_expression('5 5')!
+	ce2 := parse_expression('5 5 *')!
+	ce3 := parse_expression('5 5 * *')!
+
+	assert ce1 == ce2 && ce2 == ce3
+}