diff --git a/lib/std/collections/linkedlist.c3 b/lib/std/collections/linkedlist.c3
index e6d5e20f3..8f7a411e2 100644
--- a/lib/std/collections/linkedlist.c3
+++ b/lib/std/collections/linkedlist.c3
@@ -245,6 +245,11 @@ fn Type! LinkedList.pop(&self)
 	return self._last.value;
 }
 
+fn bool LinkedList.is_empty(&self)
+{
+	return !self._first;
+}
+
 fn Type! LinkedList.pop_front(&self)
 {
 	if (!self._first) return IteratorResult.NO_MORE_ELEMENT?;
diff --git a/lib/std/collections/priorityqueue.c3 b/lib/std/collections/priorityqueue.c3
index 4f99b18ae..e83a00cb9 100644
--- a/lib/std/collections/priorityqueue.c3
+++ b/lib/std/collections/priorityqueue.c3
@@ -46,6 +46,7 @@ fn void PrivatePriorityQueue.temp_init(&self, usz initial_capacity = 16) @inline
 	self.heap.new_init(initial_capacity, allocator::temp()) @inline;
 }
 
+
 fn void PrivatePriorityQueue.push(&self, Type element)
 {
 	self.heap.push(element);
@@ -66,6 +67,15 @@ fn void PrivatePriorityQueue.push(&self, Type element)
 	}
 }
 
+fn void PrivatePriorityQueue.remove_at(&self, usz index)
+{
+	if (index == 0)
+	{
+		self.pop()!!;
+		return;
+	}
+	self.heap.remove_at(index);
+}
 <*
  @require self != null
 *>
diff --git a/lib/std/time/time.c3 b/lib/std/time/time.c3
index 17456432c..3d9f1cfb6 100644
--- a/lib/std/time/time.c3
+++ b/lib/std/time/time.c3
@@ -6,6 +6,8 @@ distinct Duration = long;
 distinct Clock = ulong;
 distinct NanoDuration (Printable) = long;
 
+const Time FAR_FUTURE = long.max;
+const Time FAR_PAST = long.min;
 const Duration US = 1;
 const Duration MS = 1_000;
 const Duration SEC = 1_000_000;
@@ -15,6 +17,7 @@ const Duration DAY = 24 * HOUR;
 const Duration WEEK = 7 * DAY;
 const Duration MONTH = 30 * DAY;
 const Duration YEAR = 36525 * DAY / 100;
+const Duration FOREVER = long.max;
 
 fn Duration us(long l) @inline => (Duration)l * US;
 fn Duration ms(long l) @inline => (Duration)l * MS;
@@ -86,6 +89,13 @@ fn Time Time.add_hours(time, long hours) => time + (Time)(hours * (long)HOUR);
 fn Time Time.add_days(time, long days) => time + (Time)(days * (long)DAY);
 fn Time Time.add_weeks(time, long weeks) => time + (Time)(weeks * (long)WEEK);
 fn Time Time.add_duration(time, Duration duration) => time + (Time)duration;
+
+fn int Time.compare_to(time, Time other)
+{
+	if (time == other) return 0;
+	return time > other ? 1 : -1;
+}
+
 fn double Time.to_seconds(time) => (long)time / (double)SEC;
 fn Duration Time.diff_us(time, Time other) => (Duration)(time - other);
 fn double Time.diff_sec(time, Time other) => (long)time.diff_us(other) / (double)SEC;
diff --git a/releasenotes.md b/releasenotes.md
index f78475b9d..5ef5accd1 100644
--- a/releasenotes.md
+++ b/releasenotes.md
@@ -39,6 +39,7 @@
 - Wrong error message for interface methods with body #1536.
 - Empty expression block would crash compiler with debug on #1554.
 - Improve infer conversions on constants, e.g. `ZString a = foo ? "a" : "b";` #1561
+- Show error when declarations do not start with `fn` in interfaces. #1565
 
 ### Stdlib changes
 - Remove unintended print of `char[]` as String
diff --git a/src/compiler/parse_global.c b/src/compiler/parse_global.c
index a05004130..71c739bb7 100644
--- a/src/compiler/parse_global.c
+++ b/src/compiler/parse_global.c
@@ -1770,6 +1770,10 @@ INLINE bool parse_interface_body(ParseContext *c, Decl *interface)
 	{
 		AstId contracts = 0;
 		if (!parse_contracts(c, &contracts)) return poisoned_decl;
+		if (!tok_is(c, TOKEN_FN))
+		{
+			RETURN_PRINT_ERROR_HERE("Interfaces can only have function declarations, and they must start with 'fn' as usual.");
+		}
 		ASSIGN_DECL_OR_RET(Decl *interface_fn, parse_func_definition(c, contracts, FUNC_PARSE_INTERFACE), false);
 		vec_add(fns, interface_fn);
 	}
diff --git a/test/test_suite/any/interface_no_fn.c3 b/test/test_suite/any/interface_no_fn.c3
new file mode 100644
index 000000000..62f323bc1
--- /dev/null
+++ b/test/test_suite/any/interface_no_fn.c3
@@ -0,0 +1,4 @@
+interface IOp {
+	int val; // #error: Interfaces can only have function
+	int my_fn(); // missing fn
+}
\ No newline at end of file