diff --git a/b2g/config/mozconfigs/win32_gecko/nightly b/b2g/config/mozconfigs/win32_gecko/nightly
index bb6510f3059e..3f74c94ebc81 100644
--- a/b2g/config/mozconfigs/win32_gecko/nightly
+++ b/b2g/config/mozconfigs/win32_gecko/nightly
@@ -13,10 +13,6 @@ export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
diff --git a/browser/config/mozconfigs/win32/common-opt b/browser/config/mozconfigs/win32/common-opt
index e1684a8aae1c..94c5fcf92a27 100644
--- a/browser/config/mozconfigs/win32/common-opt
+++ b/browser/config/mozconfigs/win32/common-opt
@@ -18,10 +18,6 @@ export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
diff --git a/browser/config/mozconfigs/win32/debug b/browser/config/mozconfigs/win32/debug
index ad878ede5d2b..8427117e9cb5 100644
--- a/browser/config/mozconfigs/win32/debug
+++ b/browser/config/mozconfigs/win32/debug
@@ -8,10 +8,6 @@ ac_add_options --enable-metro
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
diff --git a/browser/config/mozconfigs/win64/common-opt b/browser/config/mozconfigs/win64/common-opt
index d81e366f4999..9afb969c3e58 100644
--- a/browser/config/mozconfigs/win64/common-opt
+++ b/browser/config/mozconfigs/win64/common-opt
@@ -17,9 +17,5 @@ export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
diff --git a/browser/config/mozconfigs/win64/debug b/browser/config/mozconfigs/win64/debug
index a907b9e9037a..aff6627fe6ee 100644
--- a/browser/config/mozconfigs/win64/debug
+++ b/browser/config/mozconfigs/win64/debug
@@ -11,10 +11,6 @@ ac_add_options --enable-metro
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
 
diff --git a/build/mozconfig.vs2010-common b/build/mozconfig.vs2010-common
index 9806ae24282b..ca5df2f3aa2b 100644
--- a/build/mozconfig.vs2010-common
+++ b/build/mozconfig.vs2010-common
@@ -1,8 +1,4 @@
 # Pymake needs Windows-style paths. Use cmd.exe to hack around this.
 mk_export_correct_style() {
-  if test -n "${_PYMAKE}"; then
-    mk_add_options "export $1=$(cmd.exe //c echo %$1%)"
-  else
-    mk_add_options "export $1=$(eval echo \$$1)"
-  fi
+  mk_add_options "export $1=$(cmd.exe //c echo %$1%)"
 }
diff --git a/client.mk b/client.mk
index 3723b2ee3e71..96958b61ab50 100644
--- a/client.mk
+++ b/client.mk
@@ -117,7 +117,7 @@ endef
 # before evaluation. $(shell) replacing newlines with spaces, || is always
 # followed by a space (since sed doesn't remove newlines), except on the
 # last line, so replace both '|| ' and '||'.
-MOZCONFIG_CONTENT := $(subst ||,$(CR),$(subst || ,$(CR),$(shell _PYMAKE=$(.PYMAKE) $(TOPSRCDIR)/$(MOZCONFIG_LOADER) $(TOPSRCDIR) | sed 's/$$/||/')))
+MOZCONFIG_CONTENT := $(subst ||,$(CR),$(subst || ,$(CR),$(shell $(TOPSRCDIR)/$(MOZCONFIG_LOADER) $(TOPSRCDIR) | sed 's/$$/||/')))
 $(eval $(MOZCONFIG_CONTENT))
 
 export FOUND_MOZCONFIG
diff --git a/xulrunner/config/mozconfigs/win32/xulrunner b/xulrunner/config/mozconfigs/win32/xulrunner
index 17b0cbbc2b2a..b49f37213ff3 100644
--- a/xulrunner/config/mozconfigs/win32/xulrunner
+++ b/xulrunner/config/mozconfigs/win32/xulrunner
@@ -7,10 +7,6 @@ ac_add_options --enable-application=xulrunner
 ac_add_options --enable-jemalloc
 ac_add_options --disable-tests
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD64"; then
   . $topsrcdir/build/win32/mozconfig.vs2010-win64
 else
diff --git a/xulrunner/config/mozconfigs/win64/xulrunner b/xulrunner/config/mozconfigs/win64/xulrunner
index 30dffb38265c..d2a4a740a187 100644
--- a/xulrunner/config/mozconfigs/win64/xulrunner
+++ b/xulrunner/config/mozconfigs/win64/xulrunner
@@ -10,8 +10,4 @@ ac_add_options --enable-application=xulrunner
 ac_add_options --enable-jemalloc
 ac_add_options --disable-tests
 
-if test -z "${_PYMAKE}"; then
-  mk_add_options MOZ_MAKE_FLAGS=-j1
-fi
-
 . "$topsrcdir/xulrunner/config/mozconfigs/common.override"