diff --git a/pkgs/development/compilers/rustc/1.0.0-beta.nix b/pkgs/development/compilers/rustc/1.0.0-beta.nix
index bdbca5bd30b..93359fba9f7 100644
--- a/pkgs/development/compilers/rustc/1.0.0-beta.nix
+++ b/pkgs/development/compilers/rustc/1.0.0-beta.nix
@@ -12,4 +12,5 @@ callPackage ./makeRustcDerivation.nix {
   patches = [
     ./patches/beta.patch
     ] ++ stdenv.lib.optional stdenv.needsPax ./patches/grsec.patch;
+  configureFlags = [ "--release-channel=beta" ];
 }
diff --git a/pkgs/development/compilers/rustc/makeRustcDerivation.nix b/pkgs/development/compilers/rustc/makeRustcDerivation.nix
index 913e65de59a..ae3981f1add 100644
--- a/pkgs/development/compilers/rustc/makeRustcDerivation.nix
+++ b/pkgs/development/compilers/rustc/makeRustcDerivation.nix
@@ -6,6 +6,7 @@
 , snapshotHashLinux686, snapshotHashLinux64
 , snapshotHashDarwin686, snapshotHashDarwin64
 , snapshotDate, snapshotRev
+, configureFlags ? []
 
 , patches
 }:
@@ -113,7 +114,8 @@ stdenv.mkDerivation {
     '' else "");
   };
 
-  configureFlags = [ "--enable-local-rust" "--local-rust-root=$snapshot" ]
+  configureFlags = configureFlags
+                ++ [ "--enable-local-rust" "--local-rust-root=$snapshot" ]
                 ++ stdenv.lib.optional (stdenv.cc ? clang) "--enable-clang";
 
   inherit patches;