diff --git a/pkgs/build-support/setup-hooks/install-fonts.sh b/pkgs/build-support/setup-hooks/install-fonts.sh
index 702b37a2ca43..2e63cd75f0a5 100644
--- a/pkgs/build-support/setup-hooks/install-fonts.sh
+++ b/pkgs/build-support/setup-hooks/install-fonts.sh
@@ -20,7 +20,7 @@
 # This hook also provides an `installFont` function that can be used to install
 # additional fonts of a particular extension into their respective folder.
 #
-postInstallHooks+=(installFonts)
+preInstallHooks+=(installFonts)
 
 installFont() {
   if (($# != 2)); then
diff --git a/pkgs/by-name/fi/fira-sans/package.nix b/pkgs/by-name/fi/fira-sans/package.nix
index 163e81ef8258..b65f3141fef4 100644
--- a/pkgs/by-name/fi/fira-sans/package.nix
+++ b/pkgs/by-name/fi/fira-sans/package.nix
@@ -21,7 +21,7 @@ stdenvNoCC.mkDerivation (finalAttrs: {
     stripRoot = false;
   };
 
-  postInstall = ''
+  preInstall = ''
     rm -r "__MACOSX"
   '';