diff --git a/include/proto/arg.h b/include/proto/arg.h
index 78c1105..bf33dfb 100644
--- a/include/proto/arg.h
+++ b/include/proto/arg.h
@@ -31,33 +31,33 @@
  * the number of mandatory arguments in a mask.
  */
 #define ARGM(m) \
-	(m & 15)
+	(m & ARGM_MASK)
 
 #define ARG1(m, t1) \
-	(ARGM(m) + (ARGT_##t1 << 4))
+	(ARGM(m) + (ARGT_##t1 << (ARGM_BITS)))
 
 #define ARG2(m, t1, t2) \
-	(ARG1(m, t1) + (ARGT_##t2 << 8))
+	(ARG1(m, t1) + (ARGT_##t2 << (ARGM_BITS + ARGT_BITS)))
 
 #define ARG3(m, t1, t2, t3) \
-	(ARG2(m, t1, t2) + (ARGT_##t3 << 12))
+	(ARG2(m, t1, t2) + (ARGT_##t3 << (ARGM_BITS + ARGT_BITS * 2)))
 
 #define ARG4(m, t1, t2, t3, t4) \
-	(ARG3(m, t1, t2, t3) + (ARGT_##t4 << 16))
+	(ARG3(m, t1, t2, t3) + (ARGT_##t4 << (ARGM_BITS + ARGT_BITS * 3)))
 
 #define ARG5(m, t1, t2, t3, t4, t5) \
-	(ARG4(m, t1, t2, t3, t4) + (ARGT_##t5 << 20))
+	(ARG4(m, t1, t2, t3, t4) + (ARGT_##t5 << (ARGM_BITS + ARGT_BITS * 4)))
 
 #define ARG6(m, t1, t2, t3, t4, t5, t6) \
-	(ARG5(m, t1, t2, t3, t4, t5) + (ARGT_##t6 << 24))
+	(ARG5(m, t1, t2, t3, t4, t5) + (ARGT_##t6 << (ARGM_BITS + ARGT_BITS * 5)))
 
 #define ARG7(m, t1, t2, t3, t4, t5, t6, t7) \
-	(ARG6(m, t1, t2, t3, t4, t5, t6) + (ARGT_##t7 << 28))
+	(ARG6(m, t1, t2, t3, t4, t5, t6) + (ARGT_##t7 << (ARGM_BITS + ARGT_BITS * 6)))
 
 /* This dummy arg list may be used by default when no arg is found, it helps
  * parsers by removing pointer checks.
  */
-extern struct arg empty_arg_list[8];
+extern struct arg empty_arg_list[ARGM_NBARGS];
 
 struct arg_list *arg_list_clone(const struct arg_list *orig);
 struct arg_list *arg_list_add(struct arg_list *orig, struct arg *arg, int pos);
diff --git a/include/types/arg.h b/include/types/arg.h
index 809f367..17008d9 100644
--- a/include/types/arg.h
+++ b/include/types/arg.h
@@ -28,6 +28,16 @@
 #include <common/chunk.h>
 #include <common/mini-clist.h>
 
+/* encoding of each arg type */
+#define ARGT_BITS      4
+#define ARGT_NBTYPES   (1 << ARGT_BITS)
+#define ARGT_MASK      (ARGT_NBTYPES - 1)
+
+/* encoding of the arg count */
+#define ARGM_MASK      ((1 << ARGM_BITS) - 1)
+#define ARGM_BITS      4
+#define ARGM_NBARGS    (32 - ARGM_BITS) / sizeof(int)
+
 enum {
 	ARGT_STOP = 0, /* end of the arg list */
 	ARGT_UINT,     /* unsigned integer, which is a positive integer without any sign */
@@ -45,7 +55,6 @@
 	ARGT_SRV,      /* a pointer to a server */
 	ARGT_USR,      /* a pointer to a user list */
 	ARGT_MAP,      /* a pointer to a map descriptor */
-	ARGT_NBTYPES   /* no more values past 15 */
 };
 
 /* context where arguments are used, in order to help error reporting */