diff --git a/README.md b/README.md
index 6520fd6..f859082 100644
--- a/README.md
+++ b/README.md
@@ -86,6 +86,9 @@ The following environment variables are optional and can be used to override the
 ```
 NP_DEBUG      (1 = debug msgs; 2 = 'set -e' for nix-portable)
 NP_MINIMAL    do not automatically install git
+NP_INSTALLGIT force nix-portable to use the installed git.
+NP_GITDIR     specify the directory containing the git executable.
+              (The above two are useful in environments with incompalible Git)
 NP_LOCATION   where to put the `.nix-portable` dir. (defaults to `$HOME`)
 NP_RUNTIME    which runtime to use (must be 'bwrap' or 'proot') 
 NP_BWRAP      specify the path to the bwrap executable to use
diff --git a/default.nix b/default.nix
index 47578f2..dfd8a4b 100644
--- a/default.nix
+++ b/default.nix
@@ -202,8 +202,10 @@ let
 
 
     ### detecting existing git installation
-    if [ -n "\$NP_MINIMAL" ]; then
+    if [ -n "\$NP_MINIMAL" ] || [ -n "\$NP_GITDIR" ]; then
       doInstallGit=false
+    elif [ -n "\$NP_INSTALLGIT" ]; then
+      doInstallGit=true
     else
       existingGit="\$(PATH="\$PATH_OLD:\$PATH" which git 2>&3)" || existingGit=
 
@@ -454,7 +456,15 @@ let
     fi
 
     # add git if necessary
-    \$doInstallGit && export PATH="\$PATH:${git.out}/bin"
+    if \$doInstallGit; then
+      if [ -n "\$NP_INSTALLGIT" ]; then
+        export PATH="${git.out}/bin:\$PATH"
+      else
+        export PATH="\$PATH:${git.out}/bin"
+      fi
+    elif [ -n "\$NP_GITDIR" ]; then
+      export PATH="\$NP_GITDIR:\$PATH"
+    fi