diff --git a/src/tests/util/format.cpp b/src/tests/util/format.cpp
index dcda82fa9c..21eb7827ff 100644
--- a/src/tests/util/format.cpp
+++ b/src/tests/util/format.cpp
@@ -34,6 +34,10 @@ static void tst1() {
     format f10;
     f10 += f6 + f5 + f3;
     format f11 = above(f1, above(above(f2, f3), f4));
+    format f12 = paren(format{format("a"),
+                              format("b"),
+                              format("c"),
+                              format("d")});
 
     std::vector<std::pair<std::string, format> > v =
         {{"f1",  f1},
@@ -47,6 +51,7 @@ static void tst1() {
          {"f9",  f9},
          {"f10", f10},
          {"f11", f11},
+         {"f12", f12},
         };
 
     std::for_each(v.begin(), v.end(),
@@ -56,11 +61,17 @@ static void tst1() {
                                 << "--------------------" << endl << endl;
                   });
 
-//    std::vector<std::string> ss = {"Last", "weekend's", "revelation", "that", "J.K.", "Rowling", "is", "the", "author", "of", "the", "critically", "acclaimed", "and", "--", "until", "now", "--", "commercially", "unsuccessful", "crime", "novel", "The", "Cuckoo's", "Calling", "has", "electrified", "the", "book", "world", "and", "solidified", "Rowling's", "reputation", "as", "a", "genuine", "writing", "talent:", "After", "all,", "if", "she", "can", "impress", "the", "critics", "without", "the", "benefit", "of", "her", "towering", "reputation,", "then", "surely", "her", "success", "is", "deserved."};
 
-    std::vector<std::string> ss = {"Last", "weekend's", "revelation", "that", "J.K.", "Rowling", "is", "the", "author", "of", "the", "critically", "acclaimed"};
+    std::vector<std::string> ss = {"Last", "weekend's", "revelation", "that", "J.K.", "Rowling", "is", "the", "author", "of", "the", "critically", "acclaimed", "and", "--", "until", "now", "--", "commercially", "unsuccessful", "crime", "novel", "The", "Cuckoo's", "Calling", "has", "electrified", "the", "book", "world", "and", "solidified", "Rowling's", "reputation", "as", "a", "genuine", "writing", "talent:", "After", "all,", "if", "she", "can", "impress", "the", "critics", "without", "the", "benefit", "of", "her", "towering", "reputation,", "then", "surely", "her", "success", "is", "deserved."};
 
-    std::vector<format> sl = {f1, f2, f3, f4};
+    cout << accumulate(++ss.begin(),
+               ss.end(),
+               format(*ss.begin()),
+               [](format const & result, std::string const & s) {
+                   return wrap(result, format(s));
+               });
+
+    std::vector<format> sl = {f1, f2, f3, f4, f5, f6, f7, f8, f9, f10, f11, f12};
 
     cout << "fill" << endl;
     cout << std::string(40, '=') << endl;
diff --git a/src/util/format.cpp b/src/util/format.cpp
index f7d70d70f9..d2c8bfd370 100644
--- a/src/util/format.cpp
+++ b/src/util/format.cpp
@@ -115,6 +115,9 @@ format bracket(std::string const l, format const & x, std::string const r) {
                  line(),
                  format(r)});
 }
+format paren(format const & x) {
+    return bracket("(", x, ")");
+}
 
 // wrap = <+/>
 // wrap x y = x <> (text " " :<|> line) <> y
@@ -127,8 +130,9 @@ bool format::fits(int w, sexpr const & s) {
     lean_assert(is_list(s));
     if (is_nil(s))
         return true;
-    if (w < 0)
+    if (w < 0) {
         return false;
+    }
 
     sexpr const & x = car(s);
     switch (sexpr_kind(x)) {
@@ -139,10 +143,12 @@ bool format::fits(int w, sexpr const & s) {
     case format_kind::TEXT:
     {
         size_t l = sexpr_text_length(x);
-        if(l - w > 0)
+        if(w - static_cast<int>(l) < 0) {
             return false;
-        else
-            return fits(w - l, cdr(s));
+        }
+        else {
+            return fits(w - static_cast<int>(l), cdr(s));
+        }
     }
     case format_kind::LINE:
         return true;
@@ -204,13 +210,14 @@ sexpr format::be(unsigned w, unsigned k, sexpr const & s, sexpr const & r) {
     {
         sexpr const & x = sexpr_choice_1(v);
         sexpr const & y = sexpr_choice_2(v);;
-        sexpr const & s1 = be(w, k, sexpr(sexpr(i, x), z), r);
-        if (fits(w - k, s1)) {
-            return s1;
-        } else {
-            sexpr const & s2 = be(w, k, sexpr(sexpr(i, y), z), r);
-            return s2;
+        int d = static_cast<int>(w) - static_cast<int>(k);
+        if(d >= 0) {
+            sexpr const & s1 = be(w, k, sexpr(sexpr(i, x), z), r);
+            if (fits(d, s1))
+                return s1;
         }
+        sexpr const & s2 = be(w, k, sexpr(sexpr(i, y), z), r);
+        return s2;
     }
     }
     lean_unreachable();
diff --git a/src/util/format.h b/src/util/format.h
index f8215d839f..6d26319f34 100644
--- a/src/util/format.h
+++ b/src/util/format.h
@@ -196,6 +196,7 @@ format line();
 format group(format const & f);
 format above(format const & f1, format const & f2);
 format bracket(std::string const l, format const & x, std::string const r);
+format paren(format const & x);
 format wrap(format const & f1, format const & f2);
 
 template <class InputIterator, typename F>