diff --git a/gemfiles/2.7/Gemfile b/gemfiles/2.7/Gemfile
index 8d1fbb82cd..aca548e829 100644
--- a/gemfiles/2.7/Gemfile
+++ b/gemfiles/2.7/Gemfile
@@ -8,6 +8,7 @@ gemspec path: "../.."
 
 gem "onigmo", platforms: :ruby
 gem "parser"
+gem "power_assert", "~> 2.0" # https://github.com/test-unit/test-unit/pull/329
 gem "rake-compiler"
 gem "rake"
 gem "rbs"
diff --git a/gemfiles/2.7/Gemfile.lock b/gemfiles/2.7/Gemfile.lock
index 3f3721a02e..8ee23d7208 100644
--- a/gemfiles/2.7/Gemfile.lock
+++ b/gemfiles/2.7/Gemfile.lock
@@ -30,6 +30,7 @@ PLATFORMS
 DEPENDENCIES
   onigmo
   parser
+  power_assert (~> 2.0)
   prism!
   rake
   rake-compiler
diff --git a/gemfiles/3.0/Gemfile b/gemfiles/3.0/Gemfile
index c52f90eaf8..b5499ba00e 100644
--- a/gemfiles/3.0/Gemfile
+++ b/gemfiles/3.0/Gemfile
@@ -8,6 +8,7 @@ gemspec path: "../.."
 
 gem "onigmo", platforms: :ruby
 gem "parser"
+gem "power_assert", "~> 2.0" # https://github.com/test-unit/test-unit/pull/329
 gem "rake-compiler"
 gem "rake"
 gem "rbs"
diff --git a/gemfiles/3.0/Gemfile.lock b/gemfiles/3.0/Gemfile.lock
index b7ba30c5d5..5f3934bbeb 100644
--- a/gemfiles/3.0/Gemfile.lock
+++ b/gemfiles/3.0/Gemfile.lock
@@ -38,6 +38,7 @@ PLATFORMS
 DEPENDENCIES
   onigmo
   parser
+  power_assert (~> 2.0)
   prism!
   rake
   rake-compiler