--- a/security/sandbox/linux/moz.build
+++ b/security/sandbox/linux/moz.build
@@ -73,16 +73,19 @@ SOURCES += [
     'SandboxUtil.cpp',
 ]
 
 if CONFIG['MOZ_GMP_SANDBOX']:
     SOURCES += [
         'SandboxOpenedFiles.cpp',
     ]
 
+if CONFIG['MOZ_ALSA']:
+    DEFINES['MOZ_ALSA'] = True
+
 # This copy of SafeSPrintf doesn't need to avoid the Chromium logging
 # dependency like the one in libxul does, but this way the behavior is
 # consistent.  See also the comment in SandboxLogging.h.
 SOURCES['../chromium/base/strings/safe_sprintf.cc'].flags += ['-DNDEBUG']
 
 if CONFIG['CC_TYPE'] in ('clang', 'gcc'):
     # Keep clang from warning about intentional 'switch' fallthrough in icu_utf.cc:
     SOURCES['../chromium/base/third_party/icu/icu_utf.cc'].flags += ['-Wno-implicit-fallthrough']