diff --git a/include/refcount.h b/include/refcount.h
index 785b052..533fdfe 100644
--- a/include/refcount.h
+++ b/include/refcount.h
@@ -31,10 +31,11 @@
 /* An opaque type.  You must not access these values directly.  */
 typedef unsigned int refcount_t;
 
-/* Initialize REF with REFERENCES.  */
+/* Initialize REF with REFERENCES.  REFERENCES must not be zero.  */
 static inline void
 refcount_init (refcount_t *ref, unsigned int references)
 {
+  assert (references > 0 || !"references must not be zero!");
   *ref = references;
 }
 
@@ -47,6 +48,7 @@ refcount_ref (refcount_t *ref)
   unsigned int r;
   r = __atomic_add_fetch (ref, 1, __ATOMIC_RELAXED);
   assert (r != UINT_MAX || !"refcount overflowed!");
+  assert (r != 1 || !"refcount detected use after free!");
   return r;
 }
 
@@ -101,10 +103,12 @@ union _references {
   uint64_t value;
 };
 
-/* Initialize REF with HARD and WEAK references.  */
+/* Initialize REF with HARD and WEAK references.  HARD and WEAK must
+   not both be zero.  */
 static inline void
 refcounts_init (refcounts_t *ref, uint32_t hard, uint32_t weak)
 {
+  assert ((hard != 0 || weak != 0) || !"references must not both be zero!");
   ref->references = (struct references) { .hard = hard, .weak = weak };
 }
 
@@ -119,6 +123,8 @@ refcounts_ref (refcounts_t *ref, struct references *result)
   union _references r;
   r.value = __atomic_add_fetch (&ref->value, op.value, __ATOMIC_RELAXED);
   assert (r.references.hard != UINT32_MAX || !"refcount overflowed!");
+  assert (! (r.references.hard == 1 && r.references.weak == 0)
+          || !"refcount detected use after free!");
   if (result)
     *result = r.references;
 }
@@ -208,6 +214,8 @@ refcounts_ref_weak (refcounts_t *ref, struct references *result)
   union _references r;
   r.value = __atomic_add_fetch (&ref->value, op.value, __ATOMIC_RELAXED);
   assert (r.references.weak != UINT32_MAX || !"refcount overflowed!");
+  assert (! (r.references.hard == 0 && r.references.weak == 1)
+          || !"refcount detected use after free!");
   if (result)
     *result = r.references;
 }