diff --git a/b2/subex.c b/b2/subex.c
index b073afb..06d5f77 100644
--- a/b2/subex.c
+++ b/b2/subex.c
@@ -48,7 +48,7 @@ static char *canonicalize(const char *s, char unit)
 		return stralloc(s);
 	res = stralloc("");
 	while (*s) {
-		if (*s == unit) {
+		if (*s == unit && unit != '#') {
 			assert(!seen_unit);
 			if (!s[1])
 				break;
@@ -82,7 +82,8 @@ static char *canonicalize(const char *s, char unit)
 		res_len--;
 	if (mult)
 		append_char(&res, &res_len, mult);
-	append_char(&res, &res_len, unit);
+	if (unit != '#')
+		append_char(&res, &res_len, unit);
 	return res;
 }
 
diff --git a/b2/subst.c b/b2/subst.c
index 0474ee1..a6f10db 100644
--- a/b2/subst.c
+++ b/b2/subst.c
@@ -55,9 +55,11 @@ static struct subst *alloc_subst(enum subst_type type)
 static void unit_expr(char **res, int *res_len, char unit)
 {
 	append(res, res_len, "(-?[0-9]+\\.?[0-9]*[" MULT_CHARS "]?");
-	append_char(res, res_len, unit);
+	if (unit != '#')
+		append_char(res, res_len, unit);
 	append(res, res_len, "?|-?[0-9]+[");
-	append_char(res, res_len, unit);
+	if (unit != '#')
+		append_char(res, res_len, unit);
 	append(res, res_len, MULT_CHARS "][0-9]*)");
 }
 
@@ -90,7 +92,8 @@ static char *prepare_re(const char *re, char *units)
 		case '(':
 			parens++;
 			if (re[1] == '#' && re[2]) {
-				if ((!isalpha(re[2]) && re[2] != '%') ||
+				if ((!isalpha(re[2]) &&
+				    re[2] != '%'  && re[2] != '#') ||
 				    re[3] != ')')
 					yyerrorf("invalid (#unit) syntax");
 				units[parens-1] = re[2];