diff --git a/src/option_types.hh b/src/option_types.hh
index 0f204b70..a8fd7d78 100644
--- a/src/option_types.hh
+++ b/src/option_types.hh
@@ -32,7 +32,7 @@ inline void option_from_string(StringView str, bool& opt)
         throw runtime_error("boolean values are either true, yes, false or no");
 }
 
-constexpr Codepoint list_separator = ':';
+constexpr char list_separator = ':';
 
 template<typename T, MemoryDomain domain>
 String option_to_string(const Vector<T, domain>& opt)
@@ -98,7 +98,7 @@ void option_from_string(StringView str, UnorderedMap<Key, Value, domain>& opt)
     }
 }
 
-constexpr Codepoint tuple_separator = ',';
+constexpr char tuple_separator = ',';
 
 template<size_t I, typename... Types>
 struct TupleOptionDetail
diff --git a/src/string.cc b/src/string.cc
index ba8403f7..df7bfa68 100644
--- a/src/string.cc
+++ b/src/string.cc
@@ -148,16 +148,22 @@ String expand_tabs(StringView line, CharCount tabstop, CharCount col)
 {
     String res;
     res.reserve(line.length());
-    using Utf8It = utf8::iterator<const char*>;
-    for (Utf8It it = line.begin(); it.base() < line.end(); ++it)
+    for (auto it = line.begin(), end = line.end(); it != end; )
     {
         if (*it == '\t')
         {
             CharCount end_col = (col / tabstop + 1) * tabstop;
             res += String{' ', end_col - col};
+            col = end_col;
+            ++it;
         }
         else
-            res += *it;
+        {
+            auto char_end = utf8::next(it, end);
+            res += {it, char_end};
+            ++col;
+            it = char_end;
+        }
     }
     return res;
 }
diff --git a/src/string.hh b/src/string.hh
index fba20f15..b1e51e7e 100644
--- a/src/string.hh
+++ b/src/string.hh
@@ -150,6 +150,7 @@ public:
     constexpr StringView(const char* begin, const char* end) : m_data{begin}, m_length{(int)(end - begin)} {}
     StringView(const String& str) : m_data{str.data()}, m_length{(int)str.length()} {}
     StringView(const char& c) : m_data(&c), m_length(1) {}
+    StringView(int c) = delete;
 
     [[gnu::always_inline]]
     constexpr const char* data() const { return m_data; }