diff --git a/pkgs/applications/version-management/git-and-tools/git/default.nix b/pkgs/applications/version-management/git-and-tools/git/default.nix
index fbb57a65812..7ba69a9fc18 100644
--- a/pkgs/applications/version-management/git-and-tools/git/default.nix
+++ b/pkgs/applications/version-management/git-and-tools/git/default.nix
@@ -55,7 +55,7 @@ stdenv.mkDerivation {
       # Install git-subtree.
       pushd contrib/subtree
       make
-      make install install-doc
+      make install ${stdenv.lib.optionalString withManual "install-doc"}
       popd
       rm -rf contrib/subtree