--- a/browser/config/mozconfigs/macosx-universal/common-opt
+++ b/browser/config/mozconfigs/macosx-universal/common-opt
@@ -13,15 +13,10 @@ ac_add_options --with-mozilla-api-keyfil
 # Needed to enable breakpad in application.ini
 export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
 # Treat warnings as errors (modulo ALLOW_COMPILER_WARNINGS).
 ac_add_options --enable-warnings-as-errors
 
-# Enable Widevine CDMs on MacOSX in Mozilla builds.
-# Enabled here on the assumption that downstream vendors will not be using
-# these build configs.
-ac_add_options --enable-eme=widevine
-
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1

--- a/browser/config/mozconfigs/win32/common-opt
+++ b/browser/config/mozconfigs/win32/common-opt
@@ -26,15 +26,17 @@ export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
 . $topsrcdir/build/win32/mozconfig.vs-latest
 
 # Treat warnings as errors (modulo ALLOW_COMPILER_WARNINGS).
 ac_add_options --enable-warnings-as-errors
 
-# Enable Adobe Primetime and Widevine CDMs on 32-bit Windows in Mozilla builds.
+# Enable Adobe Primetime CDM on 32-bit Windows in Mozilla builds.
 # Enabled here on the assumption that downstream vendors will not be using
 # these build configs.
-ac_add_options --enable-eme=adobe,widevine
+# Note: Widevine is automatically enabled by the build, and can be
+# disabled with -widevine.
+ac_add_options --enable-eme=+adobe
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1

--- a/browser/config/mozconfigs/win64/common-opt
+++ b/browser/config/mozconfigs/win64/common-opt
@@ -24,15 +24,17 @@ export MOZILLA_OFFICIAL=1
 
 export MOZ_TELEMETRY_REPORTING=1
 
 # Treat warnings as errors (modulo ALLOW_COMPILER_WARNINGS).
 ac_add_options --enable-warnings-as-errors
 
 . $topsrcdir/build/win64/mozconfig.vs-latest
 
-# Enable Adobe Primetime and Widevine CDMs on 64-bit Windows in Mozilla builds.
+# Enable Adobe Primetime CDM on 64-bit Windows in Mozilla builds.
 # Enabled here on the assumption that downstream vendors will not be using
 # these build configs.
-ac_add_options --enable-eme=adobe,widevine
+# Note: Widevine is automatically enabled by the build, and can be
+# disabled with -widevine.
+ac_add_options --enable-eme=+adobe
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1