diff --git a/security/nss/coreconf/Linux.mk b/security/nss/coreconf/Linux.mk
index d07f8a3c5e..854d3ca96e 100644
--- a/security/nss/coreconf/Linux.mk
+++ b/security/nss/coreconf/Linux.mk
@@ -21,7 +21,7 @@ ifeq ($(USE_PTHREADS),1)
 endif
 
 DEFAULT_COMPILER = gcc
-DEFINES += -D_DEFAULT_SOURCE -D_BSD_SOURCE
+DEFINES += -D_DEFAULT_SOURCE -D_BSD_SOURCE -D_POSIX_SOURCE
 
 ifeq ($(OS_TARGET),Android)
 ifndef ANDROID_NDK
diff --git a/security/nss/coreconf/config.gypi b/security/nss/coreconf/config.gypi
index 3b049111a8..adb344e795 100644
--- a/security/nss/coreconf/config.gypi
+++ b/security/nss/coreconf/config.gypi
@@ -357,6 +357,7 @@
               'linux',
               '_DEFAULT_SOURCE', # for <endian.h> functions, strdup, realpath, and getentropy
               '_BSD_SOURCE', # for the above in glibc <= 2.19
+              '_POSIX_SOURCE', # for <signal.h>
             ],
           }],
           [ 'OS=="dragonfly" or OS=="freebsd"', {