diff --git a/doc/install_pip.md b/doc/install_pip.md
index 2670178696fc6c09fe691edb9fafee96d4842a6a..7695e44dab7700bf2cd71b6f427b2f622f32175c 100644
--- a/doc/install_pip.md
+++ b/doc/install_pip.md
@@ -5,6 +5,14 @@ You have to use a shell on GNU/Linux or a command tool (`cmd.exe`) on Windows.
 ## GNU/Linux 
 The system must use UTF-8 locales…
 
+### Install libsodium
+
+```bash
+sudo apt install libsodium23 # Debian Buster
+sudo apt install libsodium18 # Debian Stretch
+sudo dnf install libsodium # Fedora
+```
+
 ### Install dependencies before installing
 
 ```bash
diff --git a/doc/install_pipenv.md b/doc/install_pipenv.md
index 4c386753232b2faed4d5c8d4c1ded0c56a8c31b8..50a18628b56b19753d4b33961320e4e9fc02f35e 100644
--- a/doc/install_pipenv.md
+++ b/doc/install_pipenv.md
@@ -1,5 +1,13 @@
 # Install Silkaj with Pipenv
 
+### Install libsodium
+
+```bash
+sudo apt install libsodium23 # Debian Buster
+sudo apt install libsodium18 # Debian Stretch
+sudo dnf install libsodium # Fedora
+```
+
 ### Install pipenv
 
 - [Pipenv installation instructions](https://github.com/pypa/pipenv#installation)