diff --git a/lib/system/threads.nim b/lib/system/threads.nim
index 8041b8a8f4..754d071811 100644
--- a/lib/system/threads.nim
+++ b/lib/system/threads.nim
@@ -256,8 +256,9 @@ when emulatedThreadVars:
 # we preallocate a fixed size for thread local storage, so that no heap
 # allocations are needed. Currently less than 7K are used on a 64bit machine.
 # We use ``float`` for proper alignment:
+const nimTlsSize {.intdefine.} = 8000
 type
-  ThreadLocalStorage = array[0..1_000, float]
+  ThreadLocalStorage = array[0..(nimTlsSize div sizeof(float)), float]
 
   PGcThread = ptr GcThread
   GcThread {.pure, inheritable.} = object
@@ -323,7 +324,11 @@ when not defined(useNimRtl):
 
   when emulatedThreadVars:
     if nimThreadVarsSize() > sizeof(ThreadLocalStorage):
-      echo "too large thread local storage size requested"
+      echo "too large thread local storage size requested ",
+           "(", nimThreadVarsSize(), "/", sizeof(ThreadLocalStorage), "). ",
+           "Use -d:\"nimTlsSize=", nimThreadVarsSize(),
+           "\" to preallocate sufficient storage."
+
       quit 1
 
   when hasSharedHeap and not defined(boehmgc) and not defined(gogc) and not defined(nogc):