diff --git a/src/alloc.c b/src/alloc.c
index 571d6291c2b74978a1e65c22cacf2fe9deb1c490..258a610886daab9e8c7bd2f44f911cf5ed0b981c 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 34ab179dfde36c57e67cfd4d766ede619154bccd..49f6e2390756a714f61048863037c471d13917d1 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 e9f9a9872ef8de1f3afd2e2a1e3c333e8b362c1a..332503840c9dee267e619a197d73d05d067d29e1 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