diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 3feaf7d5503..8f4adbb1082 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -32,11 +32,11 @@
   config ? null
 
 , crossSystem ? null
-, platform ? (import ./platforms.nix).pc
+, platform ? null
 }:
 
 
-let config_ = config; in # rename the function argument
+let config_ = config; platform_ = platform; in # rename the function arguments
 
 let
 
@@ -70,6 +70,10 @@ let
         then configExpr { inherit pkgs pkgsOrig; }
         else configExpr;
 
+  # Allow setting the platform in the config file. Otherwise, let's use a reasonable default (pc)
+  platform = if platform_ != null then platform_ 
+    else getConfig [ "platform" ] (import ./platforms.nix).pc;
+
   # Return an attribute from the Nixpkgs configuration file, or
   # a default value if the attribute doesn't exist.
   getConfig = attrPath: default: lib.attrByPath attrPath default config;