diff --git a/pkgs/applications/networking/browsers/firefox/builder.sh b/pkgs/applications/networking/browsers/firefox/builder.sh
index 66f1059d657..4fa7fbb84ab 100644
--- a/pkgs/applications/networking/browsers/firefox/builder.sh
+++ b/pkgs/applications/networking/browsers/firefox/builder.sh
@@ -6,6 +6,11 @@ postInstall() {
     # Strip some more stuff
     strip -S $out/lib/*/* || true
 
+    # Fix some references to /bin paths in the Firefox shell script.
+    substituteInPlace $out/bin/firefox \
+        --replace /bin/pwd "$(type -tP pwd)" \
+        --replace /bin/ls "$(type -tP ls)"
+    
     # This fixes starting Firefox when there already is a running
     # instance.  The `firefox' wrapper script actually expects to be
     # in the same directory as `run-mozilla.sh', apparently.
@@ -25,6 +30,7 @@ postInstall() {
     # Put the Firefox icon in the right place.
     ensureDir $out/lib/$libDir/chrome/icons/default
     ln -s ../../../icons/default.xpm  $out/lib/$libDir/chrome/icons/default/
+    
 }
 
 genericBuild