diff --git a/src/cmd/compile/internal/gc/order.go b/src/cmd/compile/internal/gc/order.go
index 6d235667821..0a273556cd7 100644
--- a/src/cmd/compile/internal/gc/order.go
+++ b/src/cmd/compile/internal/gc/order.go
@@ -423,7 +423,7 @@ func ordermapassign(n *Node, order *Order) {
 		// We call writebarrierfat only for values > 4 pointers long. See walk.go.
 		// TODO(mdempsky): writebarrierfat doesn't exist anymore, but removing that
 		// logic causes net/http's tests to become flaky; see CL 21242.
-		if needwritebarrier(n.Left, n.Right) && n.Left.Type.Width > int64(4*Widthptr) && !isaddrokay(n.Right) {
+		if needwritebarrier(n.Left, n.Right) && n.Left.Type.Width > int64(4*Widthptr) && n.Right != nil && !isaddrokay(n.Right) {
 			m := n.Left
 			n.Left = ordertemp(m.Type, order, false)
 			a := nod(OAS, m, n.Left)
diff --git a/src/cmd/compile/internal/gc/sinit.go b/src/cmd/compile/internal/gc/sinit.go
index 620d7c4b896..61b42450620 100644
--- a/src/cmd/compile/internal/gc/sinit.go
+++ b/src/cmd/compile/internal/gc/sinit.go
@@ -750,8 +750,13 @@ func fixedlit(ctxt initContext, kind initKind, n *Node, var_ *Node, init *Nodes)
 		switch kind {
 		case initKindStatic:
 			a = walkexpr(a, init) // add any assignments in r to top
+			if a.Op == OASWB {
+				// Static initialization never needs
+				// write barriers.
+				a.Op = OAS
+			}
 			if a.Op != OAS {
-				Fatalf("fixedlit: not as")
+				Fatalf("fixedlit: not as, is %v", a)
 			}
 			a.IsStatic = true
 		case initKindDynamic, initKindLocalCode:
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index f0f4a998920..143a2b08c6f 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -721,7 +721,8 @@ opswitch:
 			break
 		}
 
-		if n.Right == nil || iszero(n.Right) && !instrumenting {
+		if n.Right == nil {
+			// TODO(austin): Check all "implicit zeroing"
 			break
 		}
 
@@ -2255,17 +2256,20 @@ func needwritebarrier(l *Node, r *Node) bool {
 		return false
 	}
 
-	// No write barrier for implicit zeroing.
-	if r == nil {
-		return false
-	}
-
 	// No write barrier if this is a pointer to a go:notinheap
 	// type, since the write barrier's inheap(ptr) check will fail.
 	if l.Type.IsPtr() && l.Type.Elem().NotInHeap {
 		return false
 	}
 
+	// Implicit zeroing is still zeroing, so it needs write
+	// barriers. In practice, these are all to stack variables
+	// (even if isstack isn't smart enough to figure that out), so
+	// they'll be eliminated by the backend.
+	if r == nil {
+		return true
+	}
+
 	// Ignore no-op conversions when making decision.
 	// Ensures that xp = unsafe.Pointer(&x) is treated
 	// the same as xp = &x.
@@ -2273,15 +2277,13 @@ func needwritebarrier(l *Node, r *Node) bool {
 		r = r.Left
 	}
 
-	// No write barrier for zeroing or initialization to constant.
-	if iszero(r) || r.Op == OLITERAL {
-		return false
-	}
-
-	// No write barrier for storing static (read-only) data.
-	if r.Op == ONAME && strings.HasPrefix(r.Sym.Name, "statictmp_") {
-		return false
-	}
+	// TODO: We can eliminate write barriers if we know *both* the
+	// current and new content of the slot must already be shaded.
+	// We know a pointer is shaded if it's nil, or points to
+	// static data, a global (variable or function), or the stack.
+	// The nil optimization could be particularly useful for
+	// writes to just-allocated objects. Unfortunately, knowing
+	// the "current" value of the slot requires flow analysis.
 
 	// No write barrier for storing address of stack values,
 	// which are guaranteed only to be written to the stack.
@@ -2289,18 +2291,6 @@ func needwritebarrier(l *Node, r *Node) bool {
 		return false
 	}
 
-	// No write barrier for storing address of global, which
-	// is live no matter what.
-	if r.Op == OADDR && r.Left.isGlobal() {
-		return false
-	}
-
-	// No write barrier for storing global function, which is live
-	// no matter what.
-	if r.Op == ONAME && r.Class == PFUNC {
-		return false
-	}
-
 	// Otherwise, be conservative and use write barrier.
 	return true
 }
diff --git a/test/fixedbugs/issue15747.go b/test/fixedbugs/issue15747.go
index 08aa09cbd74..c0209fbf634 100644
--- a/test/fixedbugs/issue15747.go
+++ b/test/fixedbugs/issue15747.go
@@ -34,7 +34,7 @@ func f1(q *Q, xx []byte) interface{} { // ERROR "live at entry to f1: xx" "live
 //go:noinline
 func f2(d []byte, n int) (odata, res []byte, e interface{}) { // ERROR "live at entry to f2: d"
 	if n > len(d) {
-		return d, nil, &T{M: "hello"} // ERROR "live at call to newobject: d"
+		return d, nil, &T{M: "hello"} // ERROR "live at call to newobject: d" "live at call to writebarrierptr: d"
 	}
 	res = d[:n]
 	odata = d[n:]
diff --git a/test/writebarrier.go b/test/writebarrier.go
index 6fb9cd7cfee..6460a6f9dae 100644
--- a/test/writebarrier.go
+++ b/test/writebarrier.go
@@ -164,8 +164,9 @@ type T17 struct {
 }
 
 func f17(x *T17) {
-	// See golang.org/issue/13901
-	x.f = f17                      // no barrier
+	// Originally from golang.org/issue/13901, but the hybrid
+	// barrier requires both to have barriers.
+	x.f = f17                      // ERROR "write barrier"
 	x.f = func(y *T17) { *y = *x } // ERROR "write barrier"
 }
 
@@ -207,8 +208,8 @@ func f21(x *int) {
 	// Global -> heap pointer updates must have write barriers.
 	x21 = x                   // ERROR "write barrier"
 	y21.x = x                 // ERROR "write barrier"
-	x21 = &z21                // no barrier
-	y21.x = &z21              // no barrier
+	x21 = &z21                // ERROR "write barrier"
+	y21.x = &z21              // ERROR "write barrier"
 	y21 = struct{ x *int }{x} // ERROR "write barrier"
 }