diff --git a/src/lisp.h b/src/lisp.h
index d5adb8f9e49..65ea46fae1f 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -3399,6 +3399,11 @@ extern Lisp_Object Vdirectory_sep_char;
 #define min(a, b)	((a) < (b) ? (a) : (b))
 #define max(a, b)	((a) > (b) ? (a) : (b))
 
+/* Make sure we have abs defined */
+#if !defined(abs)
+#define abs(x)         ((x) < 0 ? -(x) : (x))
+#endif
+
 /* Return a fixnum or float, depending on whether VAL fits in a Lisp
    fixnum.  */