diff --git a/pkgs/build-support/fetchfossil/builder.sh b/pkgs/build-support/fetchfossil/builder.sh
index a44296543bea..89bfeb89cfc0 100644
--- a/pkgs/build-support/fetchfossil/builder.sh
+++ b/pkgs/build-support/fetchfossil/builder.sh
@@ -3,7 +3,8 @@ header "Cloning Fossil $url into $out"
 
 # Fossil, bless its adorable little heart, wants to write global configuration
 # to $HOME/.fossil. AFAICT, there is no way to disable this functionality.
-export HOME=.
+# Instead, we'll let it write to the build directory.
+export HOME=$(pwd)
 
 # We must explicitly set the admin user for the clone to something reasonable.
 fossil clone -A nobody "$url" fossil-clone.fossil