diff --git a/mozilla/build/autoconf/altoptions.m4 b/mozilla/build/autoconf/altoptions.m4
index 4d51340175b..756f5df5f58 100644
--- a/mozilla/build/autoconf/altoptions.m4
+++ b/mozilla/build/autoconf/altoptions.m4
@@ -122,7 +122,8 @@ AC_DEFUN([MOZ_CHECK_PTHREADS],
 [
 AC_MSG_CHECKING([for pthread_create in -l$1])
 echo "
-    #include <pthread.h> 
+    #include <pthread.h>
+    #include <stdlib.h>
     void *foo(void *v) { int a = 1;  } 
     int main() { 
         pthread_t t;
diff --git a/mozilla/configure.in b/mozilla/configure.in
index 9b1b0b06be9..17737395811 100644
--- a/mozilla/configure.in
+++ b/mozilla/configure.in
@@ -7892,6 +7892,7 @@ if test "$MOZ_X11"; then
     CFLAGS="$CFLAGS $XCFLAGS"
     AC_TRY_COMPILE([
         #include <stdio.h>
+        #include <stdlib.h>
         #include <X11/Xlib.h>
         #include <X11/Intrinsic.h>
     ],