diff --git a/specs/fmod_version.txt b/specs/fmod_version.txt
index e69de29bb..f5bd8cf60 100644
--- a/specs/fmod_version.txt
+++ b/specs/fmod_version.txt
@@ -0,0 +1 @@
+This version of ZDoom must be compiled with 4.26 or 4.28.