diff --git a/builder/dockerfile.alpine_319.apk.build b/builder/dockerfile.alpine_319.apk.build
index 2d4dfdc..fcec8e3 100644
--- a/builder/dockerfile.alpine_319.apk.build
+++ b/builder/dockerfile.alpine_319.apk.build
@@ -9,8 +9,14 @@ WORKDIR $HOME/kasmvncserver
 ARG KASMVNC_ALPINE_PRIVATE_KEY
 ARG KASMVNC_ALPINE_PUBLIC_KEY
 ENV APK_KEYS_DIR=/etc/apk/keys
-RUN echo -n "$KASMVNC_ALPINE_PRIVATE_KEY" > \
-  $APK_KEYS_DIR/kasmvnc_signing_key.rsa
+ENV BEGIN_PRIVATE_KEY='-----BEGIN PRIVATE KEY-----'
+ENV END_PRIVATE_KEY='-----END PRIVATE KEY-----'
+RUN if echo "$KASMVNC_ALPINE_PRIVATE_KEY" | grep -q -- "$BEGIN_PRIVATE_KEY"; then \
+      echo "$KASMVNC_ALPINE_PRIVATE_KEY" > $APK_KEYS_DIR/kasmvnc_signing_key.rsa; \
+    else \
+      echo "$BEGIN_PRIVATE_KEY\n$KASMVNC_ALPINE_PRIVATE_KEY\n$END_PRIVATE_KEY" > \
+        $APK_KEYS_DIR/kasmvnc_signing_key.rsa; \
+    fi
 RUN echo KASMVNC_ALPINE_PRIVATE_KEY "$KASMVNC_ALPINE_PRIVATE_KEY"
 RUN echo -n "$KASMVNC_ALPINE_PUBLIC_KEY" > \
   $APK_KEYS_DIR/kasmvnc_signing_key.rsa.pub