diff --git a/src/backend/threadpool.c b/src/backend/threadpool.c
index 608088137..a6d58cfe0 100644
--- a/src/backend/threadpool.c
+++ b/src/backend/threadpool.c
@@ -85,6 +85,14 @@ lumiera_threadpool_acquire_thread(enum lumiera_thread_class kind,
    }
 }
 
+void
+lumiera_threadpool_release_thread(LumieraThread thread)
+{
+  // TODO: do we need to check that index 'kind' is within range?
+  llist pool = threadpool.kind[thread->kind].pool;
+  llist_insert_head(&pool, &thread->node);
+}
+
 /*
 // Local Variables:
 // mode: C
diff --git a/src/backend/threads.c b/src/backend/threads.c
index 2c8548928..7b18ab70a 100644
--- a/src/backend/threads.c
+++ b/src/backend/threads.c
@@ -161,7 +161,7 @@ lumiera_thread_new (enum lumiera_thread_class kind,
   llist_init(&self->node);
   // self->id = (pthread_t)NULL; initialized by pthread_create()
   self->finished = finished;
-  self->type = kind;
+  self->kind = kind;
   self->state = LUMIERA_THREADSTATE_IDLE;
 
   printf("creating a thread\n");
diff --git a/src/backend/threads.h b/src/backend/threads.h
index 67c036001..ec93c4df6 100644
--- a/src/backend/threads.h
+++ b/src/backend/threads.h
@@ -105,7 +105,7 @@ struct lumiera_thread_struct
   // void* arg;
   pthread_t id;
   LumieraReccondition finished;
-  enum lumiera_thread_class type;
+  enum lumiera_thread_class kind;
   lumiera_thread_state state;
 };
 
diff --git a/tests/50threadpool.tests b/tests/50threadpool.tests
index eadb1cd32..935fb7169 100644
--- a/tests/50threadpool.tests
+++ b/tests/50threadpool.tests
@@ -4,9 +4,9 @@ TEST "Acquire/Release test" basic-acquire-release <<END
 out: start by initializing the threadpool
 out: acquiring thread 1
 out: acquiring thread 2
-out: thread 1 type=0
+out: thread 1 kind=0
 out: thread 1 state=0
-out: thread 2 type=4
+out: thread 2 kind=4
 out: thread 2 state=0
 out: releasing thread 1
 out: thread 1 has been released
diff --git a/tests/backend/test-threadpool.c b/tests/backend/test-threadpool.c
index bb9ca483c..3a514ff24 100644
--- a/tests/backend/test-threadpool.c
+++ b/tests/backend/test-threadpool.c
@@ -44,10 +44,10 @@ TEST ("basic-acquire-release")
 				      "test purpose",
 				      NULL);
 
-  printf("thread 1 type=%d\n", t1.type);
-  printf("thread 1 state=%d\n", t1.state);
-  printf("thread 2 type=%d\n", t2.type);
-  printf("thread 2 state=%d\n", t2.state);
+  printf("thread 1 kind=%d\n", t1->kind);
+  printf("thread 1 state=%d\n", t1->state);
+  printf("thread 2 kind=%d\n", t2->kind);
+  printf("thread 2 state=%d\n", t2->state);
 
   printf("releasing thread 1\n");
   lumiera_threadpool_release_thread(t1);