diff --git a/pkgs/development/compilers/dmd/default.nix b/pkgs/development/compilers/dmd/default.nix
index b15e1a9aa309..5c4e570fcb81 100644
--- a/pkgs/development/compilers/dmd/default.nix
+++ b/pkgs/development/compilers/dmd/default.nix
@@ -103,8 +103,7 @@ stdenv.mkDerivation rec {
 
   checkPhase = ''
     cd dmd
-    # https://github.com/NixOS/nixpkgs/pull/55998#issuecomment-465871846
-    #make -j$NIX_BUILD_CORES -C test -f Makefile PIC=1 CC=$CXX DMD=${pathToDmd} BUILD=release SHELL=$SHELL
+    make -j$NIX_BUILD_CORES -C test -f Makefile PIC=1 CC=$CXX DMD=${pathToDmd} BUILD=release SHELL=$SHELL
     cd ../druntime
     make -j$NIX_BUILD_CORES -f posix.mak unittest PIC=1 DMD=${pathToDmd} BUILD=release
     cd ../phobos
diff --git a/pkgs/development/compilers/ldc/default.nix b/pkgs/development/compilers/ldc/default.nix
index 043347889c84..b3cf84fdd0f8 100644
--- a/pkgs/development/compilers/ldc/default.nix
+++ b/pkgs/development/compilers/ldc/default.nix
@@ -1,4 +1,4 @@
-{ stdenv, fetchurl, cmake, ninja, llvm, llvm_8, curl, tzdata
+{ stdenv, fetchurl, cmake, ninja, llvm_5, llvm_8, curl, tzdata
 , python, libconfig, lit, gdb, unzip, darwin, bash
 , callPackage, makeWrapper, targetPackages
 , bootstrapVersion ? false
@@ -83,7 +83,7 @@ stdenv.mkDerivation rec {
   ++ stdenv.lib.optional (!bootstrapVersion && stdenv.hostPlatform.isDarwin) [
     # https://github.com/NixOS/nixpkgs/issues/57120
     # https://github.com/NixOS/nixpkgs/pull/59197#issuecomment-481972515
-    llvm
+    llvm_5
   ]
 
   ++ stdenv.lib.optional (!bootstrapVersion && !stdenv.hostPlatform.isDarwin) [
@@ -96,7 +96,7 @@ stdenv.mkDerivation rec {
   ]
 
   ++ stdenv.lib.optional (bootstrapVersion) [
-    libconfig llvm
+    libconfig llvm_5
   ]
 
   ++ stdenv.lib.optional stdenv.hostPlatform.isDarwin (with darwin.apple_sdk.frameworks; [
@@ -150,7 +150,7 @@ stdenv.mkDerivation rec {
   else
     "";
 
-  doCheck = !bootstrapVersion && !stdenv.isDarwin;
+  doCheck = !bootstrapVersion;
 
   checkPhase = stdenv.lib.optionalString doCheck ''
     # Build default lib test runners