diff --git a/lib/net/net-imap.gemspec b/lib/net/net-imap.gemspec
index 5c26a8d512..d7c341cd92 100644
--- a/lib/net/net-imap.gemspec
+++ b/lib/net/net-imap.gemspec
@@ -32,6 +32,6 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "net-protocol"
-  # spec.add_dependency "digest"
+  spec.add_dependency "digest"
   spec.add_dependency "strscan"
 end
diff --git a/lib/net/net-pop.gemspec b/lib/net/net-pop.gemspec
index 6d80e334d8..2a89f6086d 100644
--- a/lib/net/net-pop.gemspec
+++ b/lib/net/net-pop.gemspec
@@ -29,6 +29,6 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "net-protocol"
-  # spec.add_dependency "digest"
+  spec.add_dependency "digest"
   spec.add_dependency "timeout"
 end
diff --git a/lib/net/net-smtp.gemspec b/lib/net/net-smtp.gemspec
index e281b05bf6..bd0a2dd84c 100644
--- a/lib/net/net-smtp.gemspec
+++ b/lib/net/net-smtp.gemspec
@@ -30,6 +30,6 @@ Gem::Specification.new do |spec|
   spec.require_paths = ["lib"]
 
   spec.add_dependency "net-protocol"
-  # spec.add_dependency "digest"
+  spec.add_dependency "digest"
   spec.add_dependency "timeout"
 end