diff --git a/README.md b/README.md
index b1b5923..052a667 100644
--- a/README.md
+++ b/README.md
@@ -38,5 +38,11 @@ Currently supported OSes in OctaSTD are Linux, FreeBSD and OS X. Other
 systems that implement POSIX API will also work (if they don't, bug reports
 are welcome).
 
+OS X support requires Xcode 8 or newer to work. That is the first version to
+ship a Clang 3.8 based toolchain, so things will not compile with an older
+version of Xcode. Alternatively you are free to use any other supported
+compiler from other distribution channels (official Clang, homebrew gcc
+or clang, etc.).
+
 Windows is supported at least with the MinGW (gcc) and Clang compilers. MS
 Visual Studio is currently unsupported.
diff --git a/ostd/string.hh b/ostd/string.hh
index 7cd4284..c7351c4 100644
--- a/ostd/string.hh
+++ b/ostd/string.hh
@@ -504,7 +504,7 @@ public:
     StringBase &append(Size n, T c) {
         if (!n) return *this;
         reserve(p_len + n);
-        for (Size i = 0; i < n; ++n) p_buf.first()[p_len + i] = c;
+        for (Size i = 0; i < n; ++i) p_buf.first()[p_len + i] = c;
         p_len += n;
         p_buf.first()[p_len] = '\0';
         return *this;