diff --git a/pkgs/build-support/trivial-builders.nix b/pkgs/build-support/trivial-builders.nix
index 73f4d7783c4..18e49105ae7 100644
--- a/pkgs/build-support/trivial-builders.nix
+++ b/pkgs/build-support/trivial-builders.nix
@@ -8,6 +8,7 @@ rec {
   runCommand = name: env: buildCommand:
     stdenv.mkDerivation ({
       inherit name buildCommand;
+      passAsFile = [ "buildCommand" ];
     } // env);
 
 
diff --git a/pkgs/stdenv/generic/setup.sh b/pkgs/stdenv/generic/setup.sh
index 85e74461d2a..5b50167d9b9 100644
--- a/pkgs/stdenv/generic/setup.sh
+++ b/pkgs/stdenv/generic/setup.sh
@@ -827,6 +827,10 @@ showPhaseHeader() {
 
 
 genericBuild() {
+    if [ -f "$buildCommandPath" ]; then
+        . "$buildCommandPath"
+        return
+    fi
     if [ -n "$buildCommand" ]; then
         eval "$buildCommand"
         return