diff --git a/pkgs/top-level/make-tarball.nix b/pkgs/top-level/make-tarball.nix
index 62317df4163..b50f064af0c 100644
--- a/pkgs/top-level/make-tarball.nix
+++ b/pkgs/top-level/make-tarball.nix
@@ -12,7 +12,7 @@ releaseTools.sourceTarball rec {
 
   inherit officialRelease;
   version = builtins.readFile ../../.version;
-  versionSuffix = "pre${toString nixpkgs.revCount}_${nixpkgs.shortRev}";
+  versionSuffix = "pre${toString nixpkgs.revCount}.${nixpkgs.shortRev}";
 
   buildInputs = [
     lzma