diff --git a/internal/cmd/preprocessor/cmd/sidebyside_node.go b/internal/cmd/preprocessor/cmd/sidebyside_node.go
index 668670dc6..8c4f1183a 100644
--- a/internal/cmd/preprocessor/cmd/sidebyside_node.go
+++ b/internal/cmd/preprocessor/cmd/sidebyside_node.go
@@ -205,18 +205,18 @@ func (s *sidebysideNode) writeTransformTo(b *bytes.Buffer) error {
 		in, out := analyses[0], analyses[1]
 		tabs[0] = tabProps{
 			Name:     strings.ToUpper(in.Ext),
-			Language: in.Ext,
+			Language: in.Language,
 		}
 		tabs[1] = tabProps{
 			Name:     strings.ToUpper(out.Ext),
-			Language: out.Ext,
+			Language: out.Language,
 			Type:     "terminal",
 		}
 	} else {
 		for i, a := range analyses {
 			tp := &tabs[i]
 			tp.Name = a.Filepath
-			tp.Language = a.Ext
+			tp.Language = a.Language
 			if a.IsOut {
 				tp.Name = "TERMINAL"
 				tp.Type = "terminal"
diff --git a/internal/cmd/preprocessor/cmd/txtar_node.go b/internal/cmd/preprocessor/cmd/txtar_node.go
index 2870d8405..f4d6e326e 100644
--- a/internal/cmd/preprocessor/cmd/txtar_node.go
+++ b/internal/cmd/preprocessor/cmd/txtar_node.go
@@ -178,6 +178,11 @@ type filenameAnalysis struct {
 
 	// IsOut is set if the file is considered an output in the archive.
 	IsOut bool
+
+	// Language is the name used when rendering a code block for the
+	// archive file. In most cases this will be the same value as Ext
+	// but this field exists in order to allow for varying it.
+	Language string
 }
 
 // analyseTxtarArchive provides common analysis that is used by
@@ -221,6 +226,8 @@ func analyseFilename(p string) (res filenameAnalysis) {
 		// Found a .
 		res.Basename = b[:i]
 		res.Ext = b[i+1:]
+
+		res.Language = res.Ext
 	}
 	switch res.Basename {
 	case "out", "stdout":
diff --git a/internal/cmd/preprocessor/cmd/upload_node.go b/internal/cmd/preprocessor/cmd/upload_node.go
index 3b75c366a..b611514d5 100644
--- a/internal/cmd/preprocessor/cmd/upload_node.go
+++ b/internal/cmd/preprocessor/cmd/upload_node.go
@@ -43,7 +43,7 @@ func (u *uploadNode) writeTransformTo(b *bytes.Buffer) error {
 	a := u.analysis.fileNames[0]
 	props := tabProps{
 		Name:     f.Name,
-		Language: a.Ext,
+		Language: a.Language,
 	}
 	p("```%s { title=%q", props.Language, props.Name)