diff --git a/jekyll.gemspec b/jekyll.gemspec
index 37dca7a6..169d41cf 100644
--- a/jekyll.gemspec
+++ b/jekyll.gemspec
@@ -41,10 +41,10 @@ Gem::Specification.new do |s|
   s.add_runtime_dependency("kramdown",              "~> 2.3")
   s.add_runtime_dependency("kramdown-parser-gfm",   "~> 1.0")
   s.add_runtime_dependency("liquid",                "~> 4.0")
-  s.add_runtime_dependency("mercenary",             "~> 0.4.0")
+  s.add_runtime_dependency("mercenary",             ">= 0.3.6", "< 0.5")
   s.add_runtime_dependency("pathutil",              "~> 0.9")
   s.add_runtime_dependency("rouge",                 "~> 3.0")
   s.add_runtime_dependency("safe_yaml",             "~> 1.0")
-  s.add_runtime_dependency("terminal-table",        "~> 2.0")
+  s.add_runtime_dependency("terminal-table",        ">= 1.8", "< 4.0")
   s.add_runtime_dependency("webrick",               "~> 1.7")
 end