diff --git a/misc/install.func b/misc/install.func
index b3d8b62c..37f9f57f 100644
--- a/misc/install.func
+++ b/misc/install.func
@@ -878,6 +878,16 @@ setting_up_container() {
   # Remove Python EXTERNALLY-MANAGED restriction (Debian 12+, Ubuntu 23.04+)
   rm -rf /usr/lib/python3.*/EXTERNALLY-MANAGED 2>/dev/null || true
 
+  # Fix locale warnings from perl/apt (e.g. Devuan inherits host locale but hasn't generated it)
+  # C.UTF-8 is always available without locale-gen on any Linux system
+  if [[ "$PKG_MANAGER" == "apt" ]]; then
+    export DEBIAN_FRONTEND=noninteractive
+    export LC_ALL=C.UTF-8
+    export LANG=C.UTF-8
+    export LANGUAGE=C.UTF-8
+    grep -qxF 'LC_ALL=C.UTF-8' /etc/environment 2>/dev/null || echo -e 'LC_ALL=C.UTF-8\nLANG=C.UTF-8' >>/etc/environment
+  fi
+
   # Disable network wait services for faster boot
   case "$INIT_SYSTEM" in
   systemd)