diff --git a/src/runtime/asm_amd64.s b/src/runtime/asm_amd64.s
index 1a106dc1f1..e5702d074c 100644
--- a/src/runtime/asm_amd64.s
+++ b/src/runtime/asm_amd64.s
@@ -272,6 +272,7 @@ onm:
 // record an argument size. For that purpose, it has no arguments.
 TEXT runtime·morestack(SB),NOSPLIT,$0-0
 	// Cannot grow scheduler stack (m->g0).
+	get_tls(CX)
 	MOVQ	g(CX), BX
 	MOVQ	g_m(BX), BX
 	MOVQ	m_g0(BX), SI