diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index dadece6..19cda3d 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -40,7 +40,8 @@ jobs:
 
     # Static checks from this point forward. Only run on one Go version and on
     # Linux, since it's the fastest platform, and the tools behave the same.
-    - if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.18.x'
+    - name: Test third-party project builds
+      if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.18.x'
       run: |
         go install
         ./scripts/check-third-party.sh
diff --git a/position.go b/position.go
index f27c1a5..097b3a9 100644
--- a/position.go
+++ b/position.go
@@ -17,12 +17,29 @@ import (
 var printBuf1, printBuf2 bytes.Buffer
 
 // printFile prints a Go file to a buffer, while also removing non-directive
-// comments and adding extra compiler directives to obfuscate position
-// information.
+// comments and adding extra compiler directives to obfuscate position information.
 func printFile(file *ast.File) ([]byte, error) {
-	printConfig := printer.Config{Mode: printer.RawFormat}
+	if curPkg.ToObfuscate {
+		// Omit comments from the final Go code.
+		// Keep directives, as they affect the build.
+		// We do this before printing to print fewer bytes below.
+		var newComments []*ast.CommentGroup
+		for _, group := range file.Comments {
+			var newGroup ast.CommentGroup
+			for _, comment := range group.List {
+				if strings.HasPrefix(comment.Text, "//go:") {
+					newGroup.List = append(newGroup.List, comment)
+				}
+			}
+			if len(newGroup.List) > 0 {
+				newComments = append(newComments, &newGroup)
+			}
+		}
+		file.Comments = newComments
+	}
 
 	printBuf1.Reset()
+	printConfig := printer.Config{Mode: printer.RawFormat}
 	if err := printConfig.Fprint(&printBuf1, fset, file); err != nil {
 		return nil, err
 	}
@@ -71,7 +88,6 @@ func printFile(file *ast.File) ([]byte, error) {
 	// Make sure the entire file gets a zero filename by default,
 	// in case we miss any positions below.
 	// We use a //-style comment, because there might be build tags.
-	// toAdd is for /*-style comments, so add it to printBuf2 directly.
 	fmt.Fprintf(&printBuf2, "//line %s:1\n", newPrefix)
 
 	// We use an empty filename when tokenizing below.
@@ -92,10 +108,10 @@ func printFile(file *ast.File) ([]byte, error) {
 			printBuf2.Write(src[copied:])
 			return printBuf2.Bytes(), nil
 		case token.COMMENT:
-			// Omit comments from the final Go code.
-			// Keep directives, as they affect the build.
-			// This is superior to removing the comments before printing,
-			// because then the final source would have different line numbers.
+			// Omit comments from the final Go code, again.
+			// Before we removed the comments from file.Comments,
+			// but go/printer also grabs comments from some Doc ast.Node fields.
+			// TODO: is there an easy way to filter all comments at once?
 			if strings.HasPrefix(lit, "//go:") {
 				continue // directives are kept
 			}
diff --git a/scripts/cached_modfiles/github.com_andybalholm_brotli_v1.0.4.mod b/scripts/cached_modfiles/github.com_andybalholm_brotli_v1.0.4.mod
new file mode 100644
index 0000000..f43ed47
--- /dev/null
+++ b/scripts/cached_modfiles/github.com_andybalholm_brotli_v1.0.4.mod
@@ -0,0 +1,5 @@
+module test
+
+go 1.19
+
+require github.com/andybalholm/brotli v1.0.4 // indirect
diff --git a/scripts/cached_modfiles/github.com_andybalholm_brotli_v1.0.4.sum b/scripts/cached_modfiles/github.com_andybalholm_brotli_v1.0.4.sum
new file mode 100644
index 0000000..3d85808
--- /dev/null
+++ b/scripts/cached_modfiles/github.com_andybalholm_brotli_v1.0.4.sum
@@ -0,0 +1,2 @@
+github.com/andybalholm/brotli v1.0.4 h1:V7DdXeJtZscaqfNuAdSRuRFzuiKlHSC/Zh3zl9qY3JY=
+github.com/andybalholm/brotli v1.0.4/go.mod h1:fO7iG3H7G2nSZ7m0zPUDn85XEX2GTukHGRSepvi9Eig=
diff --git a/scripts/cached_modfiles/github.com_samber_lo_v1.21.0.mod b/scripts/cached_modfiles/github.com_samber_lo_v1.21.0.mod
index 1dc25e3..aca3491 100644
--- a/scripts/cached_modfiles/github.com_samber_lo_v1.21.0.mod
+++ b/scripts/cached_modfiles/github.com_samber_lo_v1.21.0.mod
@@ -1,6 +1,6 @@
 module test
 
-go 1.18
+go 1.19
 
 require (
 	github.com/samber/lo v1.21.0 // indirect
diff --git a/scripts/cached_modfiles/golang.zx2c4.com_wireguard_0.0.20220316.mod b/scripts/cached_modfiles/golang.zx2c4.com_wireguard_0.0.20220316.mod
index f1a4abd..896b0da 100644
--- a/scripts/cached_modfiles/golang.zx2c4.com_wireguard_0.0.20220316.mod
+++ b/scripts/cached_modfiles/golang.zx2c4.com_wireguard_0.0.20220316.mod
@@ -1,6 +1,6 @@
 module test
 
-go 1.18
+go 1.19
 
 require (
 	golang.org/x/crypto v0.0.0-20220315160706-3147a52a75dd // indirect
diff --git a/scripts/check-third-party.sh b/scripts/check-third-party.sh
index 303848d..1d2517a 100755
--- a/scripts/check-third-party.sh
+++ b/scripts/check-third-party.sh
@@ -19,14 +19,21 @@ modules=(
 	# google.golang.org/protobuf v1.28.0
 
 	# Wireguard helps cover networking and cryptography.
-	golang.zx2c4.com/wireguard 0.0.20220316 
+	golang.zx2c4.com/wireguard 0.0.20220316
 
 	# Lo helps cover generics.
 	# TODO: would be nice to find a more popular alternative,
 	# at least once generics are more widespread.
 	github.com/samber/lo v1.21.0
 
-	# TODO: consider a SQL driver like modernc.org/sqlite
+	# Brotli is a compression algorithm popular with HTTP.
+	# It's also transpiled from C with a gitlab.com/cznic/ccgo,
+	# so this helps stress garble with Go code that few humans would write.
+	# Unlike other ccgo-generated projects, like modernc.org/sqlite,
+	# it's relatively small without any transitive dependencies.
+	github.com/andybalholm/brotli v1.0.4
+
+	# TODO: consider github.com/mattn/go-sqlite3 to cover a DB and more cgo
 )
 
 SCRIPT_DIR=$( cd -- "$( dirname -- "${BASH_SOURCE[0]}" )" &> /dev/null && pwd )
@@ -54,16 +61,18 @@ for (( i=0; i<${#modules[@]}; i+=2 )); do
 		# We cache the files between runs and commit them in git,
 		# because each "go get module/...@version" is slow as it has to figure
 		# out where the module lives, even if GOMODCACHE is populated.
+		# Use the custom go.mod file for the rest of the commands via GOFLAGS.
+		# We should delete these cached modfiles with major Go updates,
+		# to recreate their "tidy" version with newer Go toolchains.
 		cached_modfile="${module}_${version}"
 		cached_modfile="${CACHED_MODFILES}/${cached_modfile//[^A-Za-z0-9._-]/_}.mod"
+		export GOFLAGS="${BASE_GOFLAGS} -modfile=${cached_modfile}"
+
 		if [[ ! -f "${cached_modfile}" ]]; then
 			show go mod init test
 			show go get "${module}/...@${version}"
 		fi
 
-		# Use the custom go.mod file for the rest of the commands.
-		export GOFLAGS="${BASE_GOFLAGS} -modfile=${cached_modfile}"
-
 		# Run "go build" first, to ensure the regular Go build works.
 		show go build "${module}/..."
 
diff --git a/testdata/scripts/position.txt b/testdata/scripts/position.txt
index 81d5a31..2a5ff34 100644
--- a/testdata/scripts/position.txt
+++ b/testdata/scripts/position.txt
@@ -64,6 +64,13 @@ func main() {
 	// The nested expression is needed to prevent spaces.
 	fmt.Printf("%v\n", 10*float64(3.0)/float64(4.0))
 }
+
+// Replacing `s` and `f` with obfuscated names triggered a bug in go/printer,
+// where it would move `.f` after the comment, breaking the syntax.
+func issue_573(s struct{ f int }) {
+	var _ *int = &s.f
+	/*x*/
+}
 -- garble_other_filename.go --
 package main