diff --git a/src/runtime/sys_windows_386.s b/src/runtime/sys_windows_386.s
index 2e5e828..ef8a3dd 100644
--- a/src/runtime/sys_windows_386.s
+++ b/src/runtime/sys_windows_386.s
@@ -415,12 +415,15 @@
 
 // Runs on OS stack. duration (in 100ns units) is in BX.
 TEXT runtime·usleep2HighRes(SB),NOSPLIT,$36
+	get_tls(CX)
+	CMPL	CX, $0
+	JE	gisnotset
+
 	// Want negative 100ns units.
 	NEGL	BX
 	MOVL	$-1, hi-4(SP)
 	MOVL	BX, lo-8(SP)
 
-	get_tls(CX)
 	MOVL	g(CX), CX
 	MOVL	g_m(CX), CX
 	MOVL	(m_mOS+mOS_highResTimer)(CX), CX
@@ -449,6 +452,12 @@
 
 	RET
 
+gisnotset:
+	// TLS is not configured. Call usleep2 instead.
+	MOVL	$runtime·usleep2(SB), AX
+	CALL	AX
+	RET
+
 // Runs on OS stack.
 TEXT runtime·switchtothread(SB),NOSPLIT,$0
 	MOVL	SP, BP
diff --git a/src/runtime/sys_windows_amd64.s b/src/runtime/sys_windows_amd64.s
index e9ec99a..d1690ca 100644
--- a/src/runtime/sys_windows_amd64.s
+++ b/src/runtime/sys_windows_amd64.s
@@ -454,11 +454,14 @@
 
 // Runs on OS stack. duration (in 100ns units) is in BX.
 TEXT runtime·usleep2HighRes(SB),NOSPLIT|NOFRAME,$72
+	get_tls(CX)
+	CMPQ	CX, $0
+	JE	gisnotset
+
 	MOVQ	SP, AX
 	ANDQ	$~15, SP	// alignment as per Windows requirement
 	MOVQ	AX, 64(SP)
 
-	get_tls(CX)
 	MOVQ	g(CX), CX
 	MOVQ	g_m(CX), CX
 	MOVQ	(m_mOS+mOS_highResTimer)(CX), CX	// hTimer
@@ -484,6 +487,12 @@
 	MOVQ	64(SP), SP
 	RET
 
+gisnotset:
+	// TLS is not configured. Call usleep2 instead.
+	MOVQ	$runtime·usleep2(SB), AX
+	CALL	AX
+	RET
+
 // Runs on OS stack.
 TEXT runtime·switchtothread(SB),NOSPLIT|NOFRAME,$0
 	MOVQ	SP, AX