diff --git a/config/autoconf.mk.in b/config/autoconf.mk.in
index 41f7854eeef..3a1f0d8f49e 100644
--- a/config/autoconf.mk.in
+++ b/config/autoconf.mk.in
@@ -1,3 +1,2 @@
-include $(DEPTH)/config/emptyvars.mk
 @ALLSUBSTS@
 include $(topsrcdir)/config/baseconfig.mk
diff --git a/config/emptyvars.mk.in b/config/emptyvars.mk.in
deleted file mode 100644
index 388cf2a3598..00000000000
--- a/config/emptyvars.mk.in
+++ /dev/null
@@ -1 +0,0 @@
-@ALLEMPTYSUBSTS@
diff --git a/config/moz.build b/config/moz.build
index 422455a9960..8c98eb6c345 100644
--- a/config/moz.build
+++ b/config/moz.build
@@ -6,7 +6,6 @@
 
 CONFIGURE_SUBST_FILES += [
     'autoconf.mk',
-    'emptyvars.mk',
     'doxygen.cfg',
     'makefiles/test/Makefile',
     'tests/makefiles/autodeps/Makefile',
diff --git a/js/src/config/autoconf.mk.in b/js/src/config/autoconf.mk.in
index 41f7854eeef..3a1f0d8f49e 100644
--- a/js/src/config/autoconf.mk.in
+++ b/js/src/config/autoconf.mk.in
@@ -1,3 +1,2 @@
-include $(DEPTH)/config/emptyvars.mk
 @ALLSUBSTS@
 include $(topsrcdir)/config/baseconfig.mk
diff --git a/js/src/config/emptyvars.mk.in b/js/src/config/emptyvars.mk.in
deleted file mode 100644
index 388cf2a3598..00000000000
--- a/js/src/config/emptyvars.mk.in
+++ /dev/null
@@ -1 +0,0 @@
-@ALLEMPTYSUBSTS@
diff --git a/js/src/configure.in b/js/src/configure.in
index 3ec29c04489..1e6636dc0fe 100644
--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -4384,7 +4384,7 @@ AC_SUBST(ac_configure_args)
 dnl Spit out some output
 dnl ========================================================
 
-AC_OUTPUT([js-confdefs.h Makefile config/autoconf.mk config/emptyvars.mk])
+AC_OUTPUT([js-confdefs.h Makefile config/autoconf.mk])
 
 # Produce the js-config script at configure time; see the comments for
 # 'js-config' in Makefile.in.
diff --git a/python/mozbuild/mozbuild/backend/configenvironment.py b/python/mozbuild/mozbuild/backend/configenvironment.py
index dc63edcf4ea..89d8a568429 100644
--- a/python/mozbuild/mozbuild/backend/configenvironment.py
+++ b/python/mozbuild/mozbuild/backend/configenvironment.py
@@ -86,15 +86,13 @@ class ConfigEnvironment(object):
       - ALLDEFINES contains the defines in the form #define NAME VALUE, in
         sorted order, for use in config files, for an automatic listing of
         defines.
-    and two other additional subst variables from all the other substs:
+    and another additional subst variable from all the other substs:
       - ALLSUBSTS contains the substs in the form NAME = VALUE, in sorted
         order, for use in autoconf.mk. It includes ACDEFINES, but doesn't
         include ALLDEFINES. Only substs with a VALUE are included, such that
         the resulting file doesn't change when new empty substs are added.
         This results in less invalidation of build dependencies in the case
         of autoconf.mk..
-      - ALLEMPTYSUBSTS contains the substs with an empty value, in the form
-        NAME =.
 
     ConfigEnvironment expects a "top_srcdir" subst to be set with the top
     source directory, in msys format on windows. It is used to derive a
@@ -115,8 +113,6 @@ class ConfigEnvironment(object):
             shell_escape(self.defines[name])) for name in global_defines])
         self.substs['ALLSUBSTS'] = '\n'.join(sorted(['%s = %s' % (name,
             self.substs[name]) for name in self.substs if self.substs[name]]))
-        self.substs['ALLEMPTYSUBSTS'] = '\n'.join(sorted(['%s =' % name
-            for name in self.substs if not self.substs[name]]))
         self.substs['ALLDEFINES'] = '\n'.join(sorted(['#define %s %s' % (name,
             self.defines[name]) for name in global_defines]))
 
diff --git a/python/mozbuild/mozbuild/test/backend/test_configenvironment.py b/python/mozbuild/mozbuild/test/backend/test_configenvironment.py
index dd202a3b290..a93ac9495cc 100644
--- a/python/mozbuild/mozbuild/test/backend/test_configenvironment.py
+++ b/python/mozbuild/mozbuild/test/backend/test_configenvironment.py
@@ -22,14 +22,14 @@ class ConfigEnvironment(ConfigStatus.ConfigEnvironment):
 
 class TestEnvironment(unittest.TestCase):
     def test_auto_substs(self):
-        '''Test the automatically set values of ACDEFINES, ALLDEFINES,
-        ALLSUBSTS and ALLEMPTYSUBSTS.
+        '''Test the automatically set values of ACDEFINES, ALLDEFINES
+        and ALLSUBSTS.
         '''
         env = ConfigEnvironment('.', '.',
                   defines = [ ('foo', 'bar'), ('baz', 'qux 42'),
                               ('abc', 'def'), ('extra', 'foobar') ],
                   non_global_defines = ['extra', 'ignore'],
-                  substs = [ ('FOO', 'bar'), ('FOOBAR', ''), ('ABC', 'def'),
+                  substs = [ ('FOO', 'bar'), ('ABC', 'def'),
                              ('bar', 'baz qux'), ('zzz', '"abc def"'),
                              ('qux', '') ])
         # non_global_defines should be filtered out in ACDEFINES and
@@ -47,9 +47,6 @@ ACDEFINES = -Dfoo=bar -Dbaz=qux\ 42 -Dabc=def
 FOO = bar
 bar = baz qux
 zzz = "abc def"''')
-        # ALLEMPTYSUBSTS contains all substs with no value.
-        self.assertEqual(env.substs['ALLEMPTYSUBSTS'], '''FOOBAR =
-qux =''')
 
     def test_config_file(self):
         '''Test the creation of config files.