diff --git a/google-cloud-core/lib/google/cloud/credentials.rb b/google-cloud-core/lib/google/cloud/credentials.rb
index 349b1ec93f01..53041b9857aa 100644
--- a/google-cloud-core/lib/google/cloud/credentials.rb
+++ b/google-cloud-core/lib/google/cloud/credentials.rb
@@ -29,8 +29,8 @@ class Credentials
       TOKEN_CREDENTIAL_URI = "https://accounts.google.com/o/oauth2/token"
       AUDIENCE = "https://accounts.google.com/o/oauth2/token"
       SCOPE = []
-      PATH_ENV_VARS = %w(GCLOUD_KEYFILE GOOGLE_CLOUD_KEYFILE)
-      JSON_ENV_VARS = %w(GCLOUD_KEYFILE_JSON GOOGLE_CLOUD_KEYFILE_JSON)
+      PATH_ENV_VARS = %w(GOOGLE_CLOUD_KEYFILE GCLOUD_KEYFILE)
+      JSON_ENV_VARS = %w(GOOGLE_CLOUD_KEYFILE_JSON GCLOUD_KEYFILE_JSON)
       DEFAULT_PATHS = ["~/.config/gcloud/application_default_credentials.json"]
 
       attr_accessor :client
diff --git a/google-cloud-datastore/Rakefile b/google-cloud-datastore/Rakefile
index 5ae27bcbe7e4..d81fe3fdca3d 100644
--- a/google-cloud-datastore/Rakefile
+++ b/google-cloud-datastore/Rakefile
@@ -31,7 +31,7 @@ task :acceptance, :project, :keyfile do |t, args|
   keyfile = args[:keyfile]
   keyfile ||= ENV["GCLOUD_TEST_KEYFILE"] || ENV["DATASTORE_TEST_KEYFILE"]
   if project.nil? || keyfile.nil?
-    fail "You must provide a project and keyfile. e.g. rake acceptance:datastore[test123, /path/to/keyfile.json] or DATASTORE_TEST_PROJECT=test123 DATASTORE_TEST_KEYFILE=/path/to/keyfile.json rake acceptance:datastore"
+    fail "You must provide a project and keyfile. e.g. rake acceptance[test123, /path/to/keyfile.json] or DATASTORE_TEST_PROJECT=test123 DATASTORE_TEST_KEYFILE=/path/to/keyfile.json rake acceptance"
   end
   # always overwrite when running tests
   ENV["DATASTORE_PROJECT"] = project
diff --git a/google-cloud-datastore/lib/google/cloud/datastore/credentials.rb b/google-cloud-datastore/lib/google/cloud/datastore/credentials.rb
index a237082dfe08..dac66f8a7979 100644
--- a/google-cloud-datastore/lib/google/cloud/datastore/credentials.rb
+++ b/google-cloud-datastore/lib/google/cloud/datastore/credentials.rb
@@ -28,10 +28,10 @@ module Datastore
       # @see https://developers.google.com/accounts/docs/application-default-credentials
       class Credentials < Google::Cloud::Credentials
         SCOPE = ["https://www.googleapis.com/auth/datastore"]
-        PATH_ENV_VARS = %w(DATASTORE_KEYFILE GCLOUD_KEYFILE
-                           GOOGLE_CLOUD_KEYFILE)
-        JSON_ENV_VARS = %w(DATASTORE_KEYFILE_JSON GCLOUD_KEYFILE_JSON
-                           GOOGLE_CLOUD_KEYFILE_JSON)
+        PATH_ENV_VARS = %w(DATASTORE_KEYFILE GOOGLE_CLOUD_KEYFILE
+                           GCLOUD_KEYFILE)
+        JSON_ENV_VARS = %w(DATASTORE_KEYFILE_JSON GOOGLE_CLOUD_KEYFILE_JSON
+                           GCLOUD_KEYFILE_JSON)
       end
     end
   end
diff --git a/google-cloud-datastore/lib/google/cloud/datastore/dataset.rb b/google-cloud-datastore/lib/google/cloud/datastore/dataset.rb
index 6c5c79ec2a24..abf2cf27cca9 100644
--- a/google-cloud-datastore/lib/google/cloud/datastore/dataset.rb
+++ b/google-cloud-datastore/lib/google/cloud/datastore/dataset.rb
@@ -87,8 +87,8 @@ def project
         def self.default_project
           ENV["DATASTORE_DATASET"] ||
             ENV["DATASTORE_PROJECT"] ||
-            ENV["GCLOUD_PROJECT"] ||
             ENV["GOOGLE_CLOUD_PROJECT"] ||
+            ENV["GCLOUD_PROJECT"] ||
             Google::Cloud::Core::GCE.project_id
         end
 
diff --git a/google-cloud-dns/lib/google/cloud/dns/credentials.rb b/google-cloud-dns/lib/google/cloud/dns/credentials.rb
index 9687802e9505..df194fa9f4bd 100644
--- a/google-cloud-dns/lib/google/cloud/dns/credentials.rb
+++ b/google-cloud-dns/lib/google/cloud/dns/credentials.rb
@@ -22,9 +22,9 @@ module Dns
       # @private Represents the Oauth2 signing logic for DNS.
       class Credentials < Google::Cloud::Credentials
         SCOPE = ["https://www.googleapis.com/auth/ndev.clouddns.readwrite"]
-        PATH_ENV_VARS = %w(DNS_KEYFILE GCLOUD_KEYFILE GOOGLE_CLOUD_KEYFILE)
-        JSON_ENV_VARS = %w(DNS_KEYFILE_JSON GCLOUD_KEYFILE_JSON
-                           GOOGLE_CLOUD_KEYFILE_JSON)
+        PATH_ENV_VARS = %w(DNS_KEYFILE GOOGLE_CLOUD_KEYFILE GCLOUD_KEYFILE)
+        JSON_ENV_VARS = %w(DNS_KEYFILE_JSON GOOGLE_CLOUD_KEYFILE_JSON
+                           GCLOUD_KEYFILE_JSON)
       end
     end
   end
diff --git a/google-cloud-dns/lib/google/cloud/dns/project.rb b/google-cloud-dns/lib/google/cloud/dns/project.rb
index 5f57eccdecfc..fb20a8f96691 100644
--- a/google-cloud-dns/lib/google/cloud/dns/project.rb
+++ b/google-cloud-dns/lib/google/cloud/dns/project.rb
@@ -128,8 +128,8 @@ def total_data_per_change
         # @private Default project.
         def self.default_project
           ENV["DNS_PROJECT"] ||
-            ENV["GCLOUD_PROJECT"] ||
             ENV["GOOGLE_CLOUD_PROJECT"] ||
+            ENV["GCLOUD_PROJECT"] ||
             Google::Cloud::Core::GCE.project_id
         end
 
diff --git a/google-cloud-language/lib/google/cloud/language/credentials.rb b/google-cloud-language/lib/google/cloud/language/credentials.rb
index 4223968ef9ea..bc66dcd61f83 100644
--- a/google-cloud-language/lib/google/cloud/language/credentials.rb
+++ b/google-cloud-language/lib/google/cloud/language/credentials.rb
@@ -23,9 +23,9 @@ module Language
       # @private Represents the OAuth 2.0 signing logic for Language.
       class Credentials < Google::Cloud::Credentials
         SCOPE = Google::Cloud::Language::V1beta1::LanguageServiceApi::ALL_SCOPES
-        PATH_ENV_VARS = %w(LANGUAGE_KEYFILE GCLOUD_KEYFILE GOOGLE_CLOUD_KEYFILE)
-        JSON_ENV_VARS = %w(LANGUAGE_KEYFILE_JSON GCLOUD_KEYFILE_JSON
-                           GOOGLE_CLOUD_KEYFILE_JSON)
+        PATH_ENV_VARS = %w(LANGUAGE_KEYFILE GOOGLE_CLOUD_KEYFILE GCLOUD_KEYFILE)
+        JSON_ENV_VARS = %w(LANGUAGE_KEYFILE_JSON GOOGLE_CLOUD_KEYFILE_JSON
+                           GCLOUD_KEYFILE_JSON)
       end
     end
   end