diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index d65b1a38e..cd6331f3c 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -69,7 +69,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        pgVersion: [14, 15, 16, 17]
+        pgVersion: [14, 15, 16, 17, 18]
     name: PG ${{ matrix.pgVersion }}
     runs-on: ubuntu-24.04
     defaults:
diff --git a/default.nix b/default.nix
index 9e8c5783a..c28e1cf2b 100644
--- a/default.nix
+++ b/default.nix
@@ -52,6 +52,7 @@ let
 
   postgresqlVersions =
     [
+      { name = "pg-18"; postgresql = pkgs.postgresql_18.withPackages (p: [ p.postgis p.pg_safeupdate ]); }
       { name = "pg-17"; postgresql = pkgs.postgresql_17.withPackages (p: [ p.postgis p.pg_safeupdate ]); }
       { name = "pg-16"; postgresql = pkgs.postgresql_16.withPackages (p: [ p.postgis p.pg_safeupdate ]); }
       { name = "pg-15"; postgresql = pkgs.postgresql_15.withPackages (p: [ p.postgis p.pg_safeupdate ]); }
diff --git a/nix/README.md b/nix/README.md
index aa5f8074c..58af73c40 100644
--- a/nix/README.md
+++ b/nix/README.md
@@ -95,9 +95,9 @@ postgrest-hsie-graph-modules      postgrest-with-pg-14
 postgrest-hsie-graph-symbols      postgrest-with-pg-15
 postgrest-hsie-minimal-imports    postgrest-with-pg-16
 postgrest-lint                    postgrest-with-pg-17
-postgrest-loadtest                postgrest-with-slow-pg
-postgrest-loadtest-against        postgrest-with-slow-postgrest
-postgrest-loadtest-report
+postgrest-loadtest                postgrest-with-pg-18
+postgrest-loadtest-against        postgrest-with-slow-pg
+postgrest-loadtest-report         postgrest-with-slow-postgrest
 postgrest-nixpkgs-upgrade
 ...
 
diff --git a/src/PostgREST/Config/PgVersion.hs b/src/PostgREST/Config/PgVersion.hs
index fe5b46df1..26db29e5c 100644
--- a/src/PostgREST/Config/PgVersion.hs
+++ b/src/PostgREST/Config/PgVersion.hs
@@ -5,6 +5,7 @@ module PostgREST.Config.PgVersion
   , minimumPgVersion
   , pgVersion150
   , pgVersion170
+  , pgVersion180
   ) where
 
 import qualified Data.Aeson as JSON
@@ -34,3 +35,6 @@ pgVersion150 = PgVersion 150000 "15.0" "15.0"
 
 pgVersion170 :: PgVersion
 pgVersion170 = PgVersion 170000 "17.0" "17.0"
+
+pgVersion180 :: PgVersion
+pgVersion180 = PgVersion 180000 "18.0" "18.0"
diff --git a/test/spec/Feature/Query/RpcSpec.hs b/test/spec/Feature/Query/RpcSpec.hs
index e8b6e2aa0..63e1733af 100644
--- a/test/spec/Feature/Query/RpcSpec.hs
+++ b/test/spec/Feature/Query/RpcSpec.hs
@@ -11,11 +11,13 @@ import Test.Hspec.Wai
 import Test.Hspec.Wai.JSON
 import Text.Heredoc
 
+import PostgREST.Config.PgVersion (PgVersion, pgVersion180)
+
 import Protolude  hiding (get)
 import SpecHelper
 
-spec :: SpecWith ((), Application)
-spec =
+spec :: PgVersion -> SpecWith ((), Application)
+spec actualPgVersion =
   describe "remote procedure call" $ do
     context "a proc that returns a set" $ do
       context "returns paginated results" $ do
@@ -1445,10 +1447,13 @@ spec =
       let auth = authHeaderJWT "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJyb2xlIjoicG9zdGdyZXN0X3Rlc3Rfc3VwZXJ1c2VyIiwiaWQiOiJqZG9lIn0.LQ-qx0ArBnfkwQQhIHKF5cS-lzl0gnTPI8NLoPbL5Fg" in
       it "should return http status 500" $
         request methodGet "/rpc/temp_file_limit" [auth] "" `shouldRespondWith`
-          [json|{"code":"53400","message":"temporary file size exceeds temp_file_limit (1kB)","details":null,"hint":null}|]
+          (if actualPgVersion < pgVersion180 then
+            [json|{"code":"53400","message":"temporary file size exceeds temp_file_limit (1kB)","details":null,"hint":null}|]
+           else
+            [json|{"code":"53400","message":"temporary file size exceeds \"temp_file_limit\" (1kB)","details":null,"hint":null}|]
+          )
           { matchStatus = 500
-          , matchHeaders = [ "Content-Length" <:> "105"
-                           , matchContentTypeJson ]
+          , matchHeaders = [ matchContentTypeJson ]
           }
 
     context "test table valued function with filter" $ do
diff --git a/test/spec/Main.hs b/test/spec/Main.hs
index 9d1c278b9..d51f8b0aa 100644
--- a/test/spec/Main.hs
+++ b/test/spec/Main.hs
@@ -161,7 +161,7 @@ main = do
         , ("Feature.Query.QuerySpec"                     , Feature.Query.QuerySpec.spec)
         , ("Feature.Query.RawOutputTypesSpec"            , Feature.Query.RawOutputTypesSpec.spec)
         , ("Feature.Query.RelatedQueriesSpec"            , Feature.Query.RelatedQueriesSpec.spec)
-        , ("Feature.Query.RpcSpec"                       , Feature.Query.RpcSpec.spec)
+        , ("Feature.Query.RpcSpec"                       , Feature.Query.RpcSpec.spec actualPgVersion)
         , ("Feature.Query.SingularSpec"                  , Feature.Query.SingularSpec.spec)
         , ("Feature.Query.SpreadQueriesSpec"             , Feature.Query.SpreadQueriesSpec.spec)
         , ("Feature.Query.UpdateSpec"                    , Feature.Query.UpdateSpec.spec)