diff --git a/ctl/string.cc b/ctl/string.cc
index ae5692b0f..f1bf28a50 100644
--- a/ctl/string.cc
+++ b/ctl/string.cc
@@ -47,27 +47,27 @@ string::~string() /* noexcept */
     }
 }
 
-string::string(const char* s) noexcept
+string::string(const char* s) noexcept : string()
 {
     append(s, strlen(s));
 }
 
-string::string(const string& s) noexcept
+string::string(const string& s) noexcept : string()
 {
     append(s.data(), s.size());
 }
 
-string::string(const string_view s) noexcept
+string::string(const string_view s) noexcept : string()
 {
     append(s.p, s.n);
 }
 
-string::string(size_t size, char ch) noexcept
+string::string(size_t size, char ch) noexcept : string()
 {
     resize(size, ch);
 }
 
-string::string(const char* s, size_t size) noexcept
+string::string(const char* s, size_t size) noexcept : string()
 {
     append(s, size);
 }
@@ -75,6 +75,8 @@ string::string(const char* s, size_t size) noexcept
 const char*
 string::c_str() const noexcept
 {
+    if (!size())
+        return "";
     if (size() >= capacity())
         __builtin_trap();
     if (data()[size()])
@@ -86,8 +88,9 @@ void
 string::reserve(size_t c2) noexcept
 {
     char* p2;
-    if (c2 < size())
-        c2 = size();
+    size_t n = size();
+    if (c2 < n)
+        c2 = n;
     if (ckd_add(&c2, c2, 15))
         __builtin_trap();
     c2 &= -16;
@@ -101,7 +104,6 @@ string::reserve(size_t c2) noexcept
         if (!(p2 = (char *)realloc(big()->p, c2)))
             __builtin_trap();
     }
-    size_t n = size();
     std::atomic_signal_fence(std::memory_order_seq_cst);
     set_big_capacity(c2);
     big()->n = n;
diff --git a/ctl/string.h b/ctl/string.h
index e2cb4d16b..e96ff71c0 100644
--- a/ctl/string.h
+++ b/ctl/string.h
@@ -84,7 +84,9 @@ class string
     string() noexcept
     {
         set_small_size(0);
-        small()->buf[0] = 0;
+#if 0
+        s.small()->buf[0] = 0;
+#endif
     }
 
     void swap(string& s) noexcept
@@ -100,9 +102,9 @@ class string
     {
         __builtin_memcpy(blob, __builtin_launder(s.blob), sizeof(blob));
         s.set_small_size(0);
-        /* shouldn't be necessary, but the spec says s should be left in a valid
-           state and our c_str() depends on this */
+#if 0
         s.small()->buf[0] = 0;
+#endif
     }
 
     void clear() noexcept
@@ -304,6 +306,7 @@ class string
         if (c2 > __::big_mask)
             __builtin_trap();
         *(__builtin_launder(blob) + __::sso_max) = 0x80;
+        big()->c &= ~__::big_mask;
         big()->c |= c2;
     }
 
diff --git a/test/ctl/string_test.cc b/test/ctl/string_test.cc
index 218b1b5ef..264edbbbc 100644
--- a/test/ctl/string_test.cc
+++ b/test/ctl/string_test.cc
@@ -308,6 +308,12 @@ main()
         s.append(" world");
         if (s != "hello world")
             return 63;
+        for (int i = 0; i < 4; ++i) {
+            s.append(" world");
+        }
+        if (s != "hello world world world world world") {
+            return 64;
+        }
     }
 
     // {