diff --git a/docs/networking/proxies/nginx.md b/docs/networking/proxies/nginx.md
index 9f9f72bbe..330f5fa0f 100644
--- a/docs/networking/proxies/nginx.md
+++ b/docs/networking/proxies/nginx.md
@@ -338,7 +338,7 @@ Changing these value globally or on a per-app basis will require rebuilding the
 | proxy-buffers             | `8 8k`                                | string  | Number and size of the buffers used for reading the proxied server response, for a single connection |
 | proxy-busy-buffers-size   | `16k`                                 | string  | Limits the total size of buffers that can be busy sending a response to the client while the response is not yet fully read. |
 | proxy-connect-timeout     | `60s`                                 | string  | Timeout (with units) for establishing a connection to your backend server           |
-| proxy-keepalive           | empty string                          | string  | Number of idle keepalive connections to upstream servers (disabled by default)      |
+| proxy-keepalive           | empty (disabled)                      | integer | Number of idle keepalive connections to upstream servers (disabled by default)      |
 | proxy-read-timeout        | `60s`                                 | string  | Timeout (with units) for reading response from your backend server                  |
 | proxy-send-timeout        | `60s`                                 | string  | Timeout (with units) for transmitting a request to your backend server              |
 | send-timeout              | `60s`                                 | string  | Timeout (with units) for transmitting a response to your the client                 |
diff --git a/plugins/nginx-vhosts/subcommands/set b/plugins/nginx-vhosts/subcommands/set
index 60ff463e4..e3118c4c7 100755
--- a/plugins/nginx-vhosts/subcommands/set
+++ b/plugins/nginx-vhosts/subcommands/set
@@ -25,6 +25,12 @@ cmd-nginx-set() {
     verify_app_name "$APP"
   fi
 
+  if [[ "$KEY" == "proxy-keepalive" ]] && [[ -n "$VALUE" ]]; then
+    if ! is_number "$VALUE"; then
+      dokku_log_fail "Invalid value for proxy-keepalive: must be an integer"
+    fi
+  fi
+
   if [[ -n "$VALUE" ]]; then
     dokku_log_info2_quiet "Setting ${KEY} to ${VALUE}"
     fn-plugin-property-write "nginx" "$APP" "$KEY" "$VALUE"