diff --git a/src/cmd/compile/internal/typecheck/iexport.go b/src/cmd/compile/internal/typecheck/iexport.go
index 38ac7532014..6f33ca15972 100644
--- a/src/cmd/compile/internal/typecheck/iexport.go
+++ b/src/cmd/compile/internal/typecheck/iexport.go
@@ -246,6 +246,11 @@ const (
 	interfaceType
 )
 
+const (
+	debug = false
+	magic = 0x6742937dc293105
+)
+
 func WriteExports(out *bufio.Writer) {
 	p := iexporter{
 		allPkgs:     map[*types.Pkg]bool{},
@@ -1584,6 +1589,9 @@ func (w *exportWriter) expr(n ir.Node) {
 }
 
 func (w *exportWriter) op(op ir.Op) {
+	if debug {
+		w.uint64(magic)
+	}
 	w.uint64(uint64(op))
 }
 
diff --git a/src/cmd/compile/internal/typecheck/iimport.go b/src/cmd/compile/internal/typecheck/iimport.go
index 8df75b2285f..d7c118b631d 100644
--- a/src/cmd/compile/internal/typecheck/iimport.go
+++ b/src/cmd/compile/internal/typecheck/iimport.go
@@ -1228,6 +1228,9 @@ func (r *importReader) node() ir.Node {
 }
 
 func (r *importReader) op() ir.Op {
+	if debug && r.uint64() != magic {
+		base.Fatalf("import stream has desynchronized")
+	}
 	return ir.Op(r.uint64())
 }