diff --git a/docs/building.md b/docs/building.md
index 424bac69c..fbe51bb53 100644
--- a/docs/building.md
+++ b/docs/building.md
@@ -7,6 +7,9 @@ cmake .. -DVERSION_NUM=1.0.0 -DVERSION_SUFFIX=FFFFFFF -DCMAKE_BUILD_TYPE=Release
 
 <details><summary>Linux</summary>
 
+Note that ```pkg-config``` is an optional dependency for finding libsodium,
+although we have a fallback if necessary.
+
 ### Installing dependencies on Debian and Ubuntu
 ```
 sudo apt-get install cmake g++ libsdl2-ttf-dev libsodium-dev