diff --git a/src/cmd/compile/internal/ssa/config.go b/src/cmd/compile/internal/ssa/config.go
index 13e5c50da1..b4fee75b74 100644
--- a/src/cmd/compile/internal/ssa/config.go
+++ b/src/cmd/compile/internal/ssa/config.go
@@ -291,9 +291,6 @@ func NewConfig(arch string, types Types, ctxt *obj.Link, optimize bool) *Config
 	if c.nacl {
 		c.noDuffDevice = true // Don't use Duff's device on NaCl
 
-		// runtime call clobber R12 on nacl
-		opcodeTable[OpARMCALLudiv].reg.clobbers |= 1 << 12 // R12
-
 		// Returns clobber BP on nacl/386, so the write
 		// barrier does.
 		opcodeTable[Op386LoweredWB].reg.clobbers |= 1 << 5 // BP
diff --git a/src/runtime/vlop_arm.s b/src/runtime/vlop_arm.s
index e7e8ed2e05..52143b86e7 100644
--- a/src/runtime/vlop_arm.s
+++ b/src/runtime/vlop_arm.s
@@ -102,6 +102,9 @@ TEXT runtime·_sfloatpanic(SB),NOSPLIT|NOFRAME,$0
 #define Ra	R11
 
 // Be careful: Ra == R11 will be used by the linker for synthesized instructions.
+// Note: this function does not have a frame. If it ever needs a frame,
+// the RET instruction will clobber R12 on nacl, and the compiler's register
+// allocator needs to know.
 TEXT runtime·udiv(SB),NOSPLIT|NOFRAME,$0
 	MOVBU	runtime·hardDiv(SB), Ra
 	CMP	$0, Ra