diff --git a/src/cmd/link/internal/ld/pe.go b/src/cmd/link/internal/ld/pe.go
index 16ce7bd016..00fbb170b6 100644
--- a/src/cmd/link/internal/ld/pe.go
+++ b/src/cmd/link/internal/ld/pe.go
@@ -1217,12 +1217,17 @@ func Asmbpe() {
 	// larger size, as verified with VMMap.
 
 	// Go code would be OK with 64k stacks, but we need larger stacks for cgo.
-	// That default stack reserve size affects only the main thread,
-	// for other threads we specify stack size in runtime explicitly
+	//
+	// The default stack reserve size affects only the main
+	// thread, ctrlhandler thread, and profileloop thread. For
+	// these, it must be greater than the stack size assumed by
+	// externalthreadhandler.
+	//
+	// For other threads we specify stack size in runtime explicitly
 	// (runtime knows whether cgo is enabled or not).
-	// If you change stack reserve sizes here,
-	// change STACKSIZE in runtime/cgo/gcc_windows_{386,amd64}.c and correspondent
-	// CreateThread parameter in runtime.newosproc as well.
+	// For these, the reserve must match STACKSIZE in
+	// runtime/cgo/gcc_windows_{386,amd64}.c and the correspondent
+	// CreateThread parameter in runtime.newosproc.
 	if !iscgo {
 		oh64.SizeOfStackReserve = 0x00020000
 		oh.SizeOfStackReserve = 0x00020000
diff --git a/src/runtime/sys_windows_386.s b/src/runtime/sys_windows_386.s
index e5fe88afd8..55cdcf407f 100644
--- a/src/runtime/sys_windows_386.s
+++ b/src/runtime/sys_windows_386.s
@@ -206,7 +206,8 @@ TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
 	CALL	runtime·memclr(SB)	// smashes AX,BX,CX
 	LEAL	g__size(SP), BX
 	MOVL	BX, g_m(SP)
-	LEAL	-8192(SP), CX
+
+	LEAL	-32768(SP), CX		// must be less than SizeOfStackReserve set by linker
 	MOVL	CX, (g_stack+stack_lo)(SP)
 	ADDL	$const__StackGuard, CX
 	MOVL	CX, g_stackguard0(SP)
diff --git a/src/runtime/sys_windows_amd64.s b/src/runtime/sys_windows_amd64.s
index b15eacbf32..caa18e68e9 100644
--- a/src/runtime/sys_windows_amd64.s
+++ b/src/runtime/sys_windows_amd64.s
@@ -243,7 +243,7 @@ TEXT runtime·externalthreadhandler(SB),NOSPLIT,$0
 	LEAQ	g__size(SP), BX
 	MOVQ	BX, g_m(SP)
 
-	LEAQ	-8192(SP), CX
+	LEAQ	-32768(SP), CX		// must be less than SizeOfStackReserve set by linker
 	MOVQ	CX, (g_stack+stack_lo)(SP)
 	ADDQ	$const__StackGuard, CX
 	MOVQ	CX, g_stackguard0(SP)