diff --git a/ChangeLog b/ChangeLog
index 08e62a2a52..9dd58e7c5d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+Sat May 14 09:04:34 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb (pkg_config): use xsystem consistently to set up
+	  library path environment variable as well as latter pkg-config
+	  calls.  [ruby-dev:49619] [Bug #12379]
+
 Sat May 14 00:16:54 2016  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* random.c (make_seed_value): append leading-zero-guard and get
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index e01ec6eaa8..eee42d0e51 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -1791,7 +1791,7 @@ SRC
     elsif ($PKGCONFIG ||=
            (pkgconfig = with_config("pkg-config", ("pkg-config" unless CROSS_COMPILING))) &&
            find_executable0(pkgconfig) && pkgconfig) and
-        system("#{$PKGCONFIG} --exists #{pkg}")
+        xsystem("#{$PKGCONFIG} --exists #{pkg}")
       # default to pkg-config command
       pkgconfig = $PKGCONFIG
       get = proc {|opt|