diff --git a/pkgs/development/compilers/ghc/8.4.3.nix b/pkgs/development/compilers/ghc/8.4.3.nix
index 0fecb1d2962..385c33c22ef 100644
--- a/pkgs/development/compilers/ghc/8.4.3.nix
+++ b/pkgs/development/compilers/ghc/8.4.3.nix
@@ -15,7 +15,7 @@
 
 , # If enabled, GHC will be built with the GPL-free but slower integer-simple
   # library instead of the faster but GPLed integer-gmp library.
-  enableIntegerSimple ? false, gmp ? null
+  enableIntegerSimple ? !(gmp.meta.available or false), gmp
 
 , # If enabled, use -fPIC when compiling static libs.
   enableRelocatedStaticLibs ? targetPlatform != hostPlatform
@@ -32,8 +32,6 @@
   ghcFlavour ? stdenv.lib.optionalString (targetPlatform != hostPlatform) "perf-cross"
 }:
 
-assert !enableIntegerSimple -> gmp != null;
-
 let
   inherit (bootPkgs) ghc;