diff --git a/winsup/cygwin/dcrt0.cc b/winsup/cygwin/dcrt0.cc
index e757c47ec..dee8482c2 100644
--- a/winsup/cygwin/dcrt0.cc
+++ b/winsup/cygwin/dcrt0.cc
@@ -1064,11 +1064,7 @@ _dll_crt0 ()
 	  /* Must be static since it's referenced after the stack and frame
 	     pointer registers have been changed. */
 	  static PVOID allocationbase;
-	  SIZE_T commitsize = in_forkee ? (PBYTE) fork_info->stackbase
-					  - (PBYTE) fork_info->stacklimit
-					: 0;
-	  PVOID stackaddr = create_new_main_thread_stack (allocationbase,
-							  commitsize);
+	  PVOID stackaddr = create_new_main_thread_stack (allocationbase);
 	  if (stackaddr)
 	    {
 	      /* Set stack pointer to new address.  Set frame pointer to
diff --git a/winsup/cygwin/miscfuncs.cc b/winsup/cygwin/miscfuncs.cc
index fcb082216..905c242c5 100644
--- a/winsup/cygwin/miscfuncs.cc
+++ b/winsup/cygwin/miscfuncs.cc
@@ -629,7 +629,7 @@ thread_allocator thr_alloc NO_COPY;
    maintained by the thr_alloc class.  See the description in the x86_64-only
    code in _dll_crt0 to understand why we have to do this. */
 PVOID
-create_new_main_thread_stack (PVOID &allocationbase, SIZE_T parent_commitsize)
+create_new_main_thread_stack (PVOID &allocationbase)
 {
   PIMAGE_DOS_HEADER dosheader;
   PIMAGE_NT_HEADERS ntheader;
@@ -647,10 +647,7 @@ create_new_main_thread_stack (PVOID &allocationbase, SIZE_T parent_commitsize)
   allocationbase
 	= thr_alloc.alloc (ntheader->OptionalHeader.SizeOfStackReserve);
   guardsize = wincap.def_guard_page_size ();
-  if (parent_commitsize)
-    commitsize = (SIZE_T) parent_commitsize;
-  else
-    commitsize = ntheader->OptionalHeader.SizeOfStackCommit;
+  commitsize = ntheader->OptionalHeader.SizeOfStackCommit;
   commitsize = roundup2 (commitsize, wincap.page_size ());
   if (commitsize > stacksize - guardsize - wincap.page_size ())
     commitsize = stacksize - guardsize - wincap.page_size ();
diff --git a/winsup/cygwin/miscfuncs.h b/winsup/cygwin/miscfuncs.h
index 47cef6f20..f571031eb 100644
--- a/winsup/cygwin/miscfuncs.h
+++ b/winsup/cygwin/miscfuncs.h
@@ -109,8 +109,7 @@ ssize_t __reg3 check_iovec (const struct iovec *, int, bool);
 #define check_iovec_for_write(a, b) check_iovec ((a), (b), true)
 
 #ifdef __x86_64__
-extern PVOID create_new_main_thread_stack (PVOID &allocationbase,
-					   SIZE_T parent_commitsize);
+extern PVOID create_new_main_thread_stack (PVOID &allocationbase);
 #endif
 
 extern "C" DWORD WINAPI pthread_wrapper (PVOID arg);