diff --git a/test/truffle/gems/default-bundled-gems/Gemfile b/test/truffle/gems/default-bundled-gems/Gemfile
index 1e922197ce1..c9a5b413e2c 100644
--- a/test/truffle/gems/default-bundled-gems/Gemfile
+++ b/test/truffle/gems/default-bundled-gems/Gemfile
@@ -74,7 +74,7 @@ gem "debug", "1.9.2"
 gem "matrix", "0.4.2"
 gem "minitest", "5.20.0"
 gem "net-ftp", "0.3.4"
-gem "net-imap", "0.4.19"
+gem "net-imap", "0.4.20"
 gem "net-pop", "0.1.2"
 gem "net-smtp", "0.4.0.1"
 gem "power_assert", "2.0.3"
diff --git a/test/truffle/gems/default-bundled-gems/Gemfile.lock b/test/truffle/gems/default-bundled-gems/Gemfile.lock
index 499064b4be2..891e613cf42 100644
--- a/test/truffle/gems/default-bundled-gems/Gemfile.lock
+++ b/test/truffle/gems/default-bundled-gems/Gemfile.lock
@@ -44,7 +44,7 @@ GEM
       time
     net-http (0.4.1)
       uri
-    net-imap (0.4.19)
+    net-imap (0.4.20)
       date
       net-protocol
     net-pop (0.1.2)
@@ -159,7 +159,7 @@ DEPENDENCIES
   mutex_m (= 0.2.0)
   net-ftp (= 0.3.4)
   net-http (= 0.4.1)
-  net-imap (= 0.4.19)
+  net-imap (= 0.4.20)
   net-pop (= 0.1.2)
   net-protocol (= 0.2.2)
   net-smtp (= 0.4.0.1)