diff --git a/src/cmd/dist/buildtool.go b/src/cmd/dist/buildtool.go
index a528d7aa76..0c2f51029a 100644
--- a/src/cmd/dist/buildtool.go
+++ b/src/cmd/dist/buildtool.go
@@ -85,10 +85,8 @@ var bootstrapDirs = []string{
 	"internal/unsafeheader",
 	"internal/xcoff",
 	"internal/zstd",
-	"math/big",
 	"math/bits",
 	"sort",
-	"strconv",
 }
 
 // File prefixes that are ignored by go/build anyway, and cause