diff --git a/ui/build/build.go b/ui/build/build.go
index 110ee95..1dc6dbd 100644
--- a/ui/build/build.go
+++ b/ui/build/build.go
@@ -87,6 +87,17 @@
 	// without changing the command line every time.  Avoids rebuilds
 	// when using ninja.
 	writeValueIfChanged(ctx, config, config.SoongOutDir(), "build_number.txt", buildNumber)
+
+	hostname, ok := config.environ.Get("BUILD_HOSTNAME")
+	if !ok {
+		var err error
+		hostname, err = os.Hostname()
+		if err != nil {
+			ctx.Println("Failed to read hostname:", err)
+			hostname = "unknown"
+		}
+	}
+	writeValueIfChanged(ctx, config, config.SoongOutDir(), "build_hostname.txt", hostname)
 }
 
 var combinedBuildNinjaTemplate = template.Must(template.New("combined").Parse(`
diff --git a/ui/build/kati.go b/ui/build/kati.go
index 4dfb710..acd5254 100644
--- a/ui/build/kati.go
+++ b/ui/build/kati.go
@@ -200,18 +200,10 @@
 	//     fi
 	cmd.Environment.Unset("SOONG_USE_PARTIAL_COMPILE")
 
-	hostname, ok := cmd.Environment.Get("BUILD_HOSTNAME")
 	// Unset BUILD_HOSTNAME during kati run to avoid kati rerun, kati will use BUILD_HOSTNAME from a file.
 	cmd.Environment.Unset("BUILD_HOSTNAME")
-	if !ok {
-		hostname, err = os.Hostname()
-		if err != nil {
-			ctx.Println("Failed to read hostname:", err)
-			hostname = "unknown"
-		}
-	}
-	writeValueIfChanged(ctx, config, config.SoongOutDir(), "build_hostname.txt", hostname)
-	_, ok = cmd.Environment.Get("BUILD_NUMBER")
+
+	_, ok := cmd.Environment.Get("BUILD_NUMBER")
 	// Unset BUILD_NUMBER during kati run to avoid kati rerun, kati will use BUILD_NUMBER from a file.
 	cmd.Environment.Unset("BUILD_NUMBER")
 	if ok {