diff --git a/src/alloc.c b/src/alloc.c
index 571d6291c2b..258a610886d 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -23,6 +23,11 @@ Boston, MA 02111-1307, USA.  */
 #include <signal.h>
 
 #include <config.h>
+
+#ifdef STDC_HEADERS
+#include <stdlib.h>
+#endif
+
 #include "lisp.h"
 #include "intervals.h"
 #include "puresize.h"
diff --git a/src/emacs.c b/src/emacs.c
index 34ab179dfde..49f6e239075 100644
--- a/src/emacs.c
+++ b/src/emacs.c
@@ -36,6 +36,10 @@ Boston, MA 02111-1307, USA.  */
 #include <sys/ioctl.h>
 #endif
 
+#ifdef STDC_HEADERS
+#include <stdlib.h>
+#endif
+
 #include "lisp.h"
 #include "commands.h"
 #include "intervals.h"
diff --git a/src/fileio.c b/src/fileio.c
index e9f9a9872ef..332503840c9 100644
--- a/src/fileio.c
+++ b/src/fileio.c
@@ -32,6 +32,10 @@ Boston, MA 02111-1307, USA.  */
 #include <unistd.h>
 #endif
 
+#ifdef STDC_HEADERS
+#include <stdlib.h>
+#endif
+
 #if !defined (S_ISLNK) && defined (S_IFLNK)
 #  define S_ISLNK(m) (((m) & S_IFMT) == S_IFLNK)
 #endif