diff --git a/config/nim.cfg b/config/nim.cfg
index a2a774b236..9b3172e90a 100644
--- a/config/nim.cfg
+++ b/config/nim.cfg
@@ -118,7 +118,7 @@ path="$lib/pure"
 # Configuration for the GNU C/C++ compiler:
 @if windows:
   #gcc.path = r"$nim\dist\mingw\bin"
-  @if gcc:
+  @if gcc or tcc:
     tlsEmulation:on
   @end
 @end
diff --git a/lib/pure/concurrency/threadpool.nim b/lib/pure/concurrency/threadpool.nim
index ca4f80f2a4..6ec71e912c 100644
--- a/lib/pure/concurrency/threadpool.nim
+++ b/lib/pure/concurrency/threadpool.nim
@@ -331,7 +331,7 @@ proc slave(w: ptr Worker) {.thread.} =
     await(w.taskArrived)
     # XXX Somebody needs to look into this (why does this assertion fail
     # in Visual Studio?)
-    when not defined(vcc): assert(not w.ready)
+    when not defined(vcc) and not defined(tcc): assert(not w.ready)
 
     withLock numSlavesLock:
       inc numSlavesRunning
diff --git a/lib/system/atomics.nim b/lib/system/atomics.nim
index fa3700190e..56ebde823e 100644
--- a/lib/system/atomics.nim
+++ b/lib/system/atomics.nim
@@ -241,7 +241,7 @@ when defined(vcc):
     else:
       {.error: "invalid CAS instruction".}
 
-elif defined(tcc) and not defined(windows):
+elif defined(tcc):
   when defined(amd64):
     {.emit:"""
 static int __tcc_cas(int *ptr, int oldVal, int newVal)
@@ -262,7 +262,7 @@ static int __tcc_cas(int *ptr, int oldVal, int newVal)
 }
 """.}
   else:
-    assert sizeof(int) == 4
+    #assert sizeof(int) == 4
     {.emit:"""
 static int __tcc_cas(int *ptr, int oldVal, int newVal)
 {