diff --git a/src/charset.c b/src/charset.c
index 0c9c511..0f4b0b9 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1466,9 +1466,11 @@
  * skipwhite: skip over ' ' and '\t'.
  */
     char_u *
-skipwhite(p)
-    char_u	*p;
+skipwhite(q)
+    char_u	*q;
 {
+    char_u	*p = q;
+
     while (vim_iswhite(*p)) /* skip to next non-white */
 	++p;
     return p;
@@ -1478,9 +1480,11 @@
  * skip over digits
  */
     char_u *
-skipdigits(p)
-    char_u	*p;
+skipdigits(q)
+    char_u	*q;
 {
+    char_u	*p = q;
+
     while (VIM_ISDIGIT(*p))	/* skip to next non-digit */
 	++p;
     return p;
@@ -1491,9 +1495,11 @@
  * skip over digits and hex characters
  */
     char_u *
-skiphex(p)
-    char_u	*p;
+skiphex(q)
+    char_u	*q;
 {
+    char_u	*p = q;
+
     while (vim_isxdigit(*p))	/* skip to next non-digit */
 	++p;
     return p;
@@ -1505,9 +1511,11 @@
  * skip to digit (or NUL after the string)
  */
     char_u *
-skiptodigit(p)
-    char_u	*p;
+skiptodigit(q)
+    char_u	*q;
 {
+    char_u	*p = q;
+
     while (*p != NUL && !VIM_ISDIGIT(*p))	/* skip to next digit */
 	++p;
     return p;
@@ -1517,9 +1525,11 @@
  * skip to hex character (or NUL after the string)
  */
     char_u *
-skiptohex(p)
-    char_u	*p;
+skiptohex(q)
+    char_u	*q;
 {
+    char_u	*p = q;
+
     while (*p != NUL && !vim_isxdigit(*p))	/* skip to next digit */
 	++p;
     return p;
diff --git a/src/ex_cmds.c b/src/ex_cmds.c
index 0f8af05..d700cc5 100644
--- a/src/ex_cmds.c
+++ b/src/ex_cmds.c
@@ -479,10 +479,13 @@
 	    c = *s2;
 	    (*s2) = 0;
 	    /* Sorting on number: Store the number itself. */
+	    p = s + start_col;
 	    if (sort_hex)
-		s = skiptohex(s + start_col);
+		s = skiptohex(p);
 	    else
-		s = skiptodigit(s + start_col);
+		s = skiptodigit(p);
+	    if (s > p && s[-1] == '-')
+		--s;  /* include preceding negative sign */
 	    vim_str2nr(s, NULL, NULL, sort_oct, sort_hex,
 					&nrs[lnum - eap->line1].start_col_nr, NULL);
 	    (*s2) = c;
diff --git a/src/version.c b/src/version.c
index d44083a..99b8565 100644
--- a/src/version.c
+++ b/src/version.c
@@ -677,6 +677,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    20,
+/**/
     19,
 /**/
     18,