diff --git a/src/cmd/cover/cover.go b/src/cmd/cover/cover.go
index 1748606c5e7..e04c8834bd8 100644
--- a/src/cmd/cover/cover.go
+++ b/src/cmd/cover/cover.go
@@ -386,6 +386,9 @@ func (f *File) addCounters(pos, insertPos, blockEnd token.Pos, list []ast.Stmt,
 		f.edit.Insert(f.offset(insertPos), f.newCounter(insertPos, blockEnd, 0)+";")
 		return
 	}
+	// Make a copy of the list, as we may mutate it and should leave the
+	// existing list intact.
+	list = append([]ast.Stmt(nil), list...)
 	// We have a block (statement list), but it may have several basic blocks due to the
 	// appearance of statements that affect the flow of control.
 	for {
diff --git a/src/cmd/cover/testdata/test.go b/src/cmd/cover/testdata/test.go
index 0b03ef91ab5..b794962205d 100644
--- a/src/cmd/cover/testdata/test.go
+++ b/src/cmd/cover/testdata/test.go
@@ -132,6 +132,10 @@ func testBlockRun() {
 
 func testSwitch() {
 	for i := 0; i < 5; func() { i++; check(LINE, 5) }() {
+		goto label2
+	label1:
+		goto label1
+	label2:
 		switch i {
 		case 0:
 			check(LINE, 1)