Index: src/OFThread.m
==================================================================
--- src/OFThread.m
+++ src/OFThread.m
@@ -162,10 +162,13 @@
 {
 }
 
 - start
 {
+	if (running == OF_THREAD_RUNNING)
+		@throw [OFThreadStillRunningException newWithClass: isa];
+
 	[self retain];
 
 	if (!of_thread_new(&thread, call_main, self)) {
 		[self release];
 		@throw [OFThreadStartFailedException newWithClass: isa];