diff --git a/src/resty/aws/init.lua b/src/resty/aws/init.lua
index 9bfa816..f5b7b2a 100644
--- a/src/resty/aws/init.lua
+++ b/src/resty/aws/init.lua
@@ -8,6 +8,8 @@ local execute_request = require("resty.aws.request.execute")
 local split = require("pl.utils").split
 local tablex = require("pl.tablex")
 
+local AWS_PUBLIC_DOMAIN_PATTERN = "^(.+)(%.amazonaws%.com)$"
+local AWS_VPC_ENDPOINT_DOMAIN_PATTERN = "^(.+)(%.vpce%.amazonaws%.com)$"
 
 
 -- case-insensitive lookup help.
@@ -326,8 +328,8 @@ local function generate_service_methods(service)
         -- If the endpoint is a VPC endpoint DNS hostname then we don't need to inject the region
         -- VPC endpoint DNS hostnames always contain region, see
         -- https://docs.aws.amazon.com/vpc/latest/privatelink/privatelink-access-aws-services.html#interface-endpoint-dns-hostnames
-        if not service.config._regionalEndpointInjected and not service.config.endpoint:match("^(.+)(%.vpce%.amazonaws%.com)$") then
-          local pre, post = service.config.endpoint:match("^(.+)(%.amazonaws%.com)$")
+        if not service.config._regionalEndpointInjected and not service.config.endpoint:match(AWS_VPC_ENDPOINT_DOMAIN_PATTERN) then
+          local pre, post = service.config.endpoint:match(AWS_PUBLIC_DOMAIN_PATTERN)
           service.config.endpoint = pre .. "." .. service.config.region .. post
           service.config.signingRegion = service.config.region
           service.config._regionalEndpointInjected = true