diff --git a/build/builder.go b/build/builder.go
index af695c9..ab4efcb 100644
--- a/build/builder.go
+++ b/build/builder.go
@@ -111,12 +111,14 @@
 
 // Flags adds flags for build options to fs.
 func (o *Options) Flags(fs *flag.FlagSet) {
-	fs.IntVar(&o.SizeMax, "file_limit", 2<<20, "maximum file size")
-	fs.IntVar(&o.TrigramMax, "max_trigram_count", 20000, "maximum number of trigrams per document")
-	fs.IntVar(&o.ShardMax, "shard_limit", 100<<20, "maximum corpus size for a shard")
-	fs.IntVar(&o.Parallelism, "parallelism", 4, "maximum number of parallel indexing processes.")
-	fs.StringVar(&o.IndexDir, "index", DefaultDir, "directory for search indices")
-	fs.BoolVar(&o.CTagsMustSucceed, "require_ctags", false, "If set, ctags calls must succeed.")
+	x := *o
+	x.SetDefaults()
+	fs.IntVar(&o.SizeMax, "file_limit", x.SizeMax, "maximum file size")
+	fs.IntVar(&o.TrigramMax, "max_trigram_count", x.TrigramMax, "maximum number of trigrams per document")
+	fs.IntVar(&o.ShardMax, "shard_limit", x.ShardMax, "maximum corpus size for a shard")
+	fs.IntVar(&o.Parallelism, "parallelism", x.Parallelism, "maximum number of parallel indexing processes.")
+	fs.StringVar(&o.IndexDir, "index", x.IndexDir, "directory for search indices")
+	fs.BoolVar(&o.CTagsMustSucceed, "require_ctags", x.CTagsMustSucceed, "If set, ctags calls must succeed.")
 	fs.Var(largeFilesFlag{o}, "large_file", "A glob pattern where matching files are to be index regardless of their size. You can add multiple patterns by setting this more than once.")
 }
 
@@ -163,13 +165,13 @@
 		}
 	}
 	if o.Parallelism == 0 {
-		o.Parallelism = 1
+		o.Parallelism = 4
 	}
 	if o.SizeMax == 0 {
-		o.SizeMax = 128 << 10
+		o.SizeMax = 2 << 20
 	}
 	if o.ShardMax == 0 {
-		o.ShardMax = 128 << 20
+		o.ShardMax = 100 << 20
 	}
 	if o.TrigramMax == 0 {
 		o.TrigramMax = 20000
diff --git a/build/e2e_test.go b/build/e2e_test.go
index 7019c69..ebfe053 100644
--- a/build/e2e_test.go
+++ b/build/e2e_test.go
@@ -328,9 +328,10 @@
 	defer os.RemoveAll(dir)
 
 	opts := Options{
-		IndexDir: dir,
-		ShardMax: 1024,
-		SizeMax:  1 << 20,
+		IndexDir:    dir,
+		ShardMax:    1024,
+		SizeMax:     1 << 20,
+		Parallelism: 1,
 	}
 	opts.RepositoryDescription.Name = "repo"
 	opts.SetDefaults()