Index: src/tlskey.m
==================================================================
--- src/tlskey.m
+++ src/tlskey.m
@@ -29,10 +29,11 @@
  */
 # import "runtime/private.h"
 
 static of_tlskey_t firstKey = NULL, lastKey = NULL;
 static struct SignalSemaphore semaphore;
+static bool semaphoreInitialized = false;
 
 static uint32_t
 hashFunc(const void *ptr)
 {
 	return (uint32_t)(uintptr_t)ptr;
@@ -44,11 +45,14 @@
 	return (ptr1 == ptr2);
 }
 
 OF_CONSTRUCTOR()
 {
-	InitSemaphore(&semaphore);
+	if (!semaphoreInitialized) {
+		InitSemaphore(&semaphore);
+		semaphoreInitialized = true;
+	}
 }
 #endif
 
 bool
 of_tlskey_new(of_tlskey_t *key)
@@ -56,10 +60,20 @@
 #if defined(OF_HAVE_PTHREADS)
 	return (pthread_key_create(key, NULL) == 0);
 #elif defined(OF_WINDOWS)
 	return ((*key = TlsAlloc()) != TLS_OUT_OF_INDEXES);
 #elif defined(OF_AMIGAOS)
+	if (!semaphoreInitialized) {
+		/*
+		 * We might be called from another constructor, while ours has
+		 * not run yet. This is safe, as the constructor is definitely
+		 * run before a thread is spawned.
+		 */
+		InitSemaphore(&semaphore);
+		semaphoreInitialized = true;
+	}
+
 	if ((*key = malloc(sizeof(**key))) == NULL)
 		return false;
 
 	(*key)->table = NULL;