diff --git a/base/heimbase.c b/base/heimbase.c
index 10c0d3788..b63a78cd3 100644
--- a/base/heimbase.c
+++ b/base/heimbase.c
@@ -297,6 +297,28 @@ heim_base_once_f(heim_base_once_t *once, void *ctx, void (*func)(void *))
 #ifdef HAVE_DISPATCH_DISPATCH_H
     dispatch_once_f(once, ctx, func);
 #else
-    #error "write heim_base_once_t"
+    static HEIMDAL_MUTEX mutex = HEIMDAL_MUTEX_INITIALIZER;
+    HEIMDAL_MUTEX_lock(&mutex);
+    if (*once == 0) {
+	*once = 1;
+	HEIMDAL_MUTEX_unlock(&mutex);
+	func(ctx);
+	HEIMDAL_MUTEX_lock(&mutex);
+	*once = 2;
+	HEIMDAL_MUTEX_unlock(&mutex);
+    } else if (*once == 2) {
+	HEIMDAL_MUTEX_unlock(&mutex);
+    } else {
+	HEIMDAL_MUTEX_unlock(&mutex);
+	while (1) {
+	    struct timeval tv = { 0, 1000 };
+	    select(0, NULL, NULL, NULL, &tv);
+	    HEIMDAL_MUTEX_lock(&mutex);
+	    if (*once == 2)
+		break;
+	    HEIMDAL_MUTEX_unlock(&mutex);
+	}
+	HEIMDAL_MUTEX_unlock(&mutex);
+    }
 #endif
 }