diff --git a/Gemfile.lock b/Gemfile.lock
index a71564d..bd26be9 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -12,7 +12,6 @@ GEM
     json (2.3.0)
     rake (13.0.1)
     rdoc (6.2.1)
-    redcarpet (3.5.0)
     rspec (3.9.0)
       rspec-core (~> 3.9.0)
       rspec-expectations (~> 3.9.0)
@@ -26,12 +25,11 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.9.0)
     rspec-support (3.9.2)
-    simplecov (0.15.0)
+    simplecov (0.15.1)
       docile (~> 1.1.0)
       json (>= 1.8, < 3)
       simplecov-html (~> 0.10.0)
     simplecov-html (0.10.2)
-    syntax (1.2.2)
     yard (0.9.24)
 
 PLATFORMS
@@ -43,7 +41,7 @@ DEPENDENCIES
   rdoc
   rscons!
   rspec
-  simplecov
+  simplecov (~> 0.15.0)
   yard
 
 BUNDLED WITH
diff --git a/rscons.gemspec b/rscons.gemspec
index c150c65..2566a9e 100644
--- a/rscons.gemspec
+++ b/rscons.gemspec
@@ -22,7 +22,7 @@ Gem::Specification.new do |gem|
 
   gem.add_development_dependency "rspec"
   gem.add_development_dependency "rake"
-  gem.add_development_dependency "simplecov"
+  gem.add_development_dependency "simplecov", "~> 0.15.0"
   gem.add_development_dependency "yard"
   gem.add_development_dependency "rdoc"
 end