diff --git a/src/runtime/testdata/testprog/syscall_windows.go b/src/runtime/testdata/testprog/syscall_windows.go
index b4b66441b8..71bf384dc1 100644
--- a/src/runtime/testdata/testprog/syscall_windows.go
+++ b/src/runtime/testdata/testprog/syscall_windows.go
@@ -66,5 +66,8 @@ func StackMemory() {
 	if err != nil {
 		panic(err)
 	}
-	print((mem2 - mem1) / threadCount)
+	// assumes that this process creates 1 thread for each
+	// thread locked goroutine plus extra 5 threads
+	// like sysmon and others
+	print((mem2 - mem1) / (threadCount + 5))
 }
diff --git a/src/runtime/testdata/testprogcgo/stack_windows.go b/src/runtime/testdata/testprogcgo/stack_windows.go
index 846297a960..0be1126bee 100644
--- a/src/runtime/testdata/testprogcgo/stack_windows.go
+++ b/src/runtime/testdata/testprogcgo/stack_windows.go
@@ -50,5 +50,8 @@ func StackMemory() {
 	if err != nil {
 		panic(err)
 	}
-	print((mem2 - mem1) / threadCount)
+	// assumes that this process creates 1 thread for each
+	// thread locked goroutine plus extra 5 threads
+	// like sysmon and others
+	print((mem2 - mem1) / (threadCount + 5))
 }