diff --git a/lib/system/memalloc.nim b/lib/system/memalloc.nim
index 879a1f06616c..a61e335f481c 100644
--- a/lib/system/memalloc.nim
+++ b/lib/system/memalloc.nim
@@ -116,9 +116,6 @@ when hasAlloc and not defined(js):
     ##
     ## See also:
     ## * `create <#create,typedesc>`_
-    static:
-      when sizeof(T) <= 0:
-        {.fatal: "createU does not support types T where sizeof(T) == 0".}
     cast[ptr T](alloc(T.sizeof * size))
 
   template alloc0*(size: Natural): pointer =
@@ -144,9 +141,6 @@ when hasAlloc and not defined(js):
     ##
     ## The allocated memory belongs to its allocating thread!
     ## Use `createShared <#createShared,typedesc>`_ to allocate from a shared heap.
-    static:
-      when sizeof(T) <= 0:
-        {.fatal: "create does not support types T where sizeof(T) == 0".}
     cast[ptr T](alloc0(sizeof(T) * size))
 
   template realloc*(p: pointer, newSize: Natural): pointer =
diff --git a/tests/stdlib/tsystem.nim b/tests/stdlib/tsystem.nim
index a90a1d1d9f29..786e7a432b42 100644
--- a/tests/stdlib/tsystem.nim
+++ b/tests/stdlib/tsystem.nim
@@ -101,3 +101,10 @@ block:
   reset(y)
   doAssert y.b == {}
 
+block: # bug #20516
+  type Foo = object
+    x {.bitsize:4.}: uint
+    y {.bitsize:4.}: uint
+
+  when not defined(js):
+    let a = create(Foo)