7 files changed, 10 insertions, 15 deletions
diff --git a/pkgs/servers/amqp/qpid-cpp/default.nix b/pkgs/servers/amqp/qpid-cpp/default.nix
index bb7f7def077..97c1ec90ed1 100644
--- a/pkgs/servers/amqp/qpid-cpp/default.nix
+++ b/pkgs/servers/amqp/qpid-cpp/default.nix
@@ -33,7 +33,7 @@ let
       sed -i '/management/d' CMakeLists.txt
     '';
 
-    NIX_CFLAGS_COMPILE = [
+    NIX_CFLAGS_COMPILE = toString [
       "-Wno-error=deprecated-declarations"
       "-Wno-error=int-in-bool-context"
       "-Wno-error=maybe-uninitialized"
diff --git a/pkgs/servers/computing/torque/default.nix b/pkgs/servers/computing/torque/default.nix
index 5e78fe742ac..8eb12a1b811 100644
--- a/pkgs/servers/computing/torque/default.nix
+++ b/pkgs/servers/computing/torque/default.nix
@@ -25,9 +25,7 @@ stdenv.mkDerivation rec {
   enableParallelBuilding = true;
 
   # added to fix build with gcc7
-  NIX_CFLAGS_COMPILE = [
-    "-Wno-error" "-fpermissive"
-  ];
+  NIX_CFLAGS_COMPILE = "-Wno-error -fpermissive";
 
   postPatch = ''
     substituteInPlace Makefile.am \
diff --git a/pkgs/servers/http/openresty/default.nix b/pkgs/servers/http/openresty/default.nix
index 53773302963..328db9ec986 100644
--- a/pkgs/servers/http/openresty/default.nix
+++ b/pkgs/servers/http/openresty/default.nix
@@ -15,7 +15,7 @@ stdenv.mkDerivation rec {
   buildInputs = [ openssl zlib pcre libxml2 libxslt gd geoip postgresql ];
   nativeBuildInputs = [ perl ];
 
-  NIX_CFLAGS_COMPILE = ["-I${libxml2.dev}/include/libxml2"];
+  NIX_CFLAGS_COMPILE = "-I${libxml2.dev}/include/libxml2";
 
   preConfigure = ''
     patchShebangs .
diff --git a/pkgs/servers/http/tengine/default.nix b/pkgs/servers/http/tengine/default.nix
index 379a5c242f7..1467b1577f9 100644
--- a/pkgs/servers/http/tengine/default.nix
+++ b/pkgs/servers/http/tengine/default.nix
@@ -84,10 +84,8 @@ stdenv.mkDerivation rec {
     ++ optional (with stdenv.hostPlatform; isLinux || isFreeBSD) "--with-file-aio"
     ++ map (mod: "--add-module=${mod.src}") modules;
 
-  NIX_CFLAGS_COMPILE = [
-    "-I${libxml2.dev}/include/libxml2"
-    "-Wno-error=implicit-fallthrough"
-  ] ++ optional stdenv.isDarwin "-Wno-error=deprecated-declarations";
+  NIX_CFLAGS_COMPILE = "-I${libxml2.dev}/include/libxml2 -Wno-error=implicit-fallthrough"
+    + optionalString stdenv.isDarwin " -Wno-error=deprecated-declarations";
 
   preConfigure = (concatMapStringsSep "\n" (mod: mod.preConfigure or "") modules);
 
diff --git a/pkgs/servers/mail/opensmtpd/extras.nix b/pkgs/servers/mail/opensmtpd/extras.nix
index f7ed6382a7b..5a5fc537d6e 100644
--- a/pkgs/servers/mail/opensmtpd/extras.nix
+++ b/pkgs/servers/mail/opensmtpd/extras.nix
@@ -76,11 +76,10 @@ stdenv.mkDerivation rec {
     "--with-table-redis"
   ];
 
-  NIX_CFLAGS_COMPILE =
-    stdenv.lib.optional enableRedis
+  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString enableRedis
       "-I${hiredis}/include/hiredis -lhiredis"
-    ++ stdenv.lib.optional enableMysql
-      "-L${libmysqlclient}/lib/mysql";
+    + stdenv.lib.optionalString enableMysql
+      " -L${libmysqlclient}/lib/mysql";
 
   meta = with stdenv.lib; {
     homepage = https://www.opensmtpd.org/;
diff --git a/pkgs/servers/mail/postfix/default.nix b/pkgs/servers/mail/postfix/default.nix
index b3345f9420c..c0e6252a551 100644
--- a/pkgs/servers/mail/postfix/default.nix
+++ b/pkgs/servers/mail/postfix/default.nix
@@ -79,7 +79,7 @@ in stdenv.mkDerivation rec {
     make makefiles CCARGS='${ccargs}' AUXLIBS='${auxlibs}'
   '';
 
-  NIX_LDFLAGS = lib.optional withLDAP "-llber";
+  NIX_LDFLAGS = lib.optionalString withLDAP "-llber";
 
   installTargets = [ "non-interactive-package" ];
 
diff --git a/pkgs/servers/nosql/mongodb/default.nix b/pkgs/servers/nosql/mongodb/default.nix
index 4c4ac4c5cb6..c2ae83f3e8a 100644
--- a/pkgs/servers/nosql/mongodb/default.nix
+++ b/pkgs/servers/nosql/mongodb/default.nix
@@ -66,7 +66,7 @@ in stdenv.mkDerivation {
       --replace 'engine("wiredTiger")' 'engine("mmapv1")'
   '';
 
-  NIX_CFLAGS_COMPILE = stdenv.lib.optional stdenv.cc.isClang "-Wno-unused-command-line-argument";
+  NIX_CFLAGS_COMPILE = stdenv.lib.optionalString stdenv.cc.isClang "-Wno-unused-command-line-argument";
 
   sconsFlags = [
     "--release"