diff --git a/pkgs/development/compilers/gcc/6/default.nix b/pkgs/development/compilers/gcc/6/default.nix
index c75472e73008..151dc96b2426 100644
--- a/pkgs/development/compilers/gcc/6/default.nix
+++ b/pkgs/development/compilers/gcc/6/default.nix
@@ -430,7 +430,7 @@ stdenv.mkDerivation ({
     CC_FOR_TARGET = "${targetPlatform.config}-gcc";
     NM_FOR_TARGET = "${targetPlatform.config}-nm";
     CXX_FOR_TARGET = "${targetPlatform.config}-g++";
-    # If we are making a cross compiler, cross != null
+    # If we are making a cross compiler, targetPlatform != hostPlatform
     NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
     dontStrip = true;
     configureFlags =
diff --git a/pkgs/development/compilers/gcc/7/default.nix b/pkgs/development/compilers/gcc/7/default.nix
index c201ca6373b7..7335c784a957 100644
--- a/pkgs/development/compilers/gcc/7/default.nix
+++ b/pkgs/development/compilers/gcc/7/default.nix
@@ -105,7 +105,7 @@ let version = "7.2.0";
         gccFpu = platform.gcc.fpu or null;
         gccFloat = platform.gcc.float or null;
         gccMode = platform.gcc.mode or null;
-     in
+      in
         optional (gccArch != null) "--with-arch=${gccArch}" ++
         optional (gccCpu != null) "--with-cpu=${gccCpu}" ++
         optional (gccAbi != null) "--with-abi=${gccAbi}" ++
@@ -426,7 +426,7 @@ stdenv.mkDerivation ({
     NM_FOR_TARGET = "${targetPlatform.config}-nm";
     CXX_FOR_TARGET = "${targetPlatform.config}-g++";
     # If we are making a cross compiler, targetPlatform != hostPlatform
-    NIX_CC_CROSS = if targetPlatform == hostPlatform then "${stdenv.ccCross}" else "";
+    NIX_CC_CROSS = optionalString (targetPlatform == hostPlatform) builtins.toString stdenv.cc;
     dontStrip = true;
     configureFlags =
       optional (!enableMultilib) "--disable-multilib" ++