diff --git a/.gitignore b/.gitignore
index 7fde878..a864bfb 100644
--- a/.gitignore
+++ b/.gitignore
@@ -3,6 +3,7 @@
 .bundle
 .config
 .ruby-version
+.tool-versions
 .yardoc
 .idea/
 enumerize.iml
diff --git a/.tool-versions b/.tool-versions
deleted file mode 100644
index 59511e1..0000000
--- a/.tool-versions
+++ /dev/null
@@ -1 +0,0 @@
-ruby 2.7.8
diff --git a/Gemfile.mongo_mapper b/Gemfile.mongo_mapper
index 2eb7ae9..b68d562 100644
--- a/Gemfile.mongo_mapper
+++ b/Gemfile.mongo_mapper
@@ -3,4 +3,7 @@ eval_gemfile('Gemfile.global')
 gem 'minitest', '~> 5.8'
 gem 'rails',    github: 'rails/rails', branch: '7-0-stable', require: false
 gem 'mongo_mapper'
-gem 'sqlite3', :platform => [:ruby, :mswin, :mingw]
+
+# This Rails version has a pessimistic version constraint on sqlite3:
+# https://github.com/rails/rails/blob/7-0-stable/Gemfile#L148
+gem 'sqlite3', '~> 1.6', '>= 1.6.6', :platform => [:ruby, :mswin, :mingw]
diff --git a/Gemfile.rails61 b/Gemfile.rails61
index 3910089..02b724c 100644
--- a/Gemfile.rails61
+++ b/Gemfile.rails61
@@ -3,4 +3,7 @@ eval_gemfile('Gemfile.global')
 gem 'minitest', '~> 5.8'
 gem 'rails',    github: 'rails/rails', branch: '6-1-stable', require: false
 gem 'mongoid',  github: 'mongodb/mongoid'
-gem 'sqlite3', :platform => [:ruby, :mswin, :mingw]
+
+# This Rails version has a pessimistic version constraint on sqlite3:
+# https://github.com/rails/rails/blob/6-1-stable/Gemfile#L143
+gem 'sqlite3', '~> 1.4', :platform => [:ruby, :mswin, :mingw]
diff --git a/Gemfile.rails70 b/Gemfile.rails70
index 53e9bed..7487748 100644
--- a/Gemfile.rails70
+++ b/Gemfile.rails70
@@ -5,4 +5,6 @@ gem 'rails',    github: 'rails/rails', branch: '7-0-stable', require: false
 
 gem 'mongoid',  github: 'mongodb/mongoid'
 
-gem 'sqlite3', :platform => [:ruby, :mswin, :mingw]
+# This Rails version has a pessimistic version constraint on sqlite3:
+https://github.com/rails/rails/blob/7-0-stable/Gemfile#L148
+gem 'sqlite3', '~> 1.6', '>= 1.6.6', :platform => [:ruby, :mswin, :mingw]