src/cmd/5l/noop.c      |  5 +++--
 src/cmd/8l/pass.c      |  2 +-
 src/pkg/runtime/proc.c |  6 ++++--
 test/stack.go          | 27 +++++++++++++++++++++++++++

diff --git a/src/cmd/5l/noop.c b/src/cmd/5l/noop.c
index 925984d7561ba8322d1e2948994713d327189f08..a9439c27a6a3b71c7a0cb358213c72be0d00688c 100644
--- a/src/cmd/5l/noop.c
+++ b/src/cmd/5l/noop.c
@@ -330,13 +330,14 @@ 						p->from.type = D_REG;
 						p->from.reg = 1;
 						p->reg = 2;
 					}
-	
+
 					// MOVW.LO		$autosize, R1
 					p = appendp(p);
 					p->as = AMOVW;
 					p->scond = C_SCOND_LO;
 					p->from.type = D_CONST;
-					p->from.offset = 0;
+					/* 160 comes from 3 calls (3*8) 4 safes (4*8) and 104 guard */
+					p->from.offset = autosize+160;
 					p->to.type = D_REG;
 					p->to.reg = 1;
 	
diff --git a/src/cmd/8l/pass.c b/src/cmd/8l/pass.c
index c3f1f4736fc142e0c8daea6b819142907916b87f..878a73dac9bd7f01f0b787b7a3abc9336b0e51cf 100644
--- a/src/cmd/8l/pass.c
+++ b/src/cmd/8l/pass.c
@@ -517,7 +517,7 @@ 			p->as = AMOVL;
 			p->to.type = D_DX;
 			/* 160 comes from 3 calls (3*8) 4 safes (4*8) and 104 guard */
 			p->from.type = D_CONST;
-			if(autoffset+160 > 4096)
+			if(autoffset+160+cursym->text->to.offset2 > 4096)
 				p->from.offset = (autoffset+160) & ~7LL;
 
 			p = appendp(p);	// save arg size in AX
diff --git a/src/pkg/runtime/proc.c b/src/pkg/runtime/proc.c
index 62872d989c9d1577152386b74a3e67e0a5dda6b9..998cbc7bc221df03ad30cc2a256852ba2185aac3 100644
--- a/src/pkg/runtime/proc.c
+++ b/src/pkg/runtime/proc.c
@@ -723,8 +723,10 @@ 	framesize = m->moreframesize;
 	argsize = m->moreargsize;
 	g1 = m->curg;
 
-	if(m->morebuf.sp < g1->stackguard - StackGuard)
-		runtime·throw("split stack overflow");
+	if(m->morebuf.sp < g1->stackguard - StackGuard) {
+		runtime·printf("runtime: split stack overflow: %p < %p\n", m->morebuf.sp, g1->stackguard - StackGuard);
+		runtime·throw("runtime: split stack overflow");
+	}
 
 	reflectcall = framesize==1;
 	if(reflectcall)
diff --git a/test/stack.go b/test/stack.go
index 816b555a4c8849618a26ad9498fead3878c52d6b..1fd57161ff2903aff1bd3b15ff38cff561e8f8a1 100644
--- a/test/stack.go
+++ b/test/stack.go
@@ -30,6 +30,32 @@ 		panic("fail")
 	}
 }
 
+func f0() {
+	// likely to make a new stack for f0,
+	// because the call to f1 puts 3000 bytes
+	// in our frame.
+	f1()
+}
+
+func f1() [3000]byte {
+	// likely to make a new stack for f1,
+	// because 3000 bytes were used by f0
+	// and we need 3000 more for the call
+	// to f2.  if the call to morestack in f1
+	// does not pass the frame size, the new
+	// stack (default size 5k) will not be big
+	// enough for the frame, and the morestack
+	// check in f2 will die, if we get that far 
+	// without faulting.
+	f2()
+	return [3000]byte{}
+}
+
+func f2() [3000]byte {
+	// just take up space
+	return [3000]byte{}
+}
+
 var c = make(chan int)
 var t T
 var b = []byte{1, 2, 3, 4, 5, 6, 7, 8, 9, 10}
@@ -40,6 +66,7 @@ 	if len(ss) != len(b) {
 		panic("bad []byte -> string")
 	}
 	go g(c, t)
+	f0()
 	s := <-c
 	if s != len(t) {
 		println("bad go", s)