diff --git a/hphp/compiler/expression/unary_op_expression.cpp b/hphp/compiler/expression/unary_op_expression.cpp
index 98d78b4cc..f47ceb2b8 100644
--- a/hphp/compiler/expression/unary_op_expression.cpp
+++ b/hphp/compiler/expression/unary_op_expression.cpp
@@ -237,21 +237,30 @@ bool UnaryOpExpression::preCompute(CVarRef value, Variant &result) {
                 *result.asCell());
         break;
       case '~':
-        result = value.bitNot(); break;
+        tvSet(*value.asCell(), *result.asTypedValue());
+        cellBitNot(*result.asCell());
+        break;
       case '@':
-        result = value; break;
+        result = value;
+        break;
       case T_INT_CAST:
-        result = value.toInt64(); break;
+        result = value.toInt64();
+        break;
       case T_DOUBLE_CAST:
-        result = toDouble(value); break;
+        result = toDouble(value);
+        break;
       case T_STRING_CAST:
-        result = toString(value); break;
+        result = toString(value);
+        break;
       case T_BOOL_CAST:
-        result = toBoolean(value); break;
+        result = toBoolean(value);
+        break;
       case T_EMPTY:
-        result = empty(value); break;
+        result = empty(value);
+        break;
       case T_ISSET:
-        result = isset(value); break;
+        result = isset(value);
+        break;
       case T_INC:
       case T_DEC:
         assert(false);
diff --git a/hphp/runtime/base/tv_arith.cpp b/hphp/runtime/base/tv_arith.cpp
index 97a68fd78..26cc75add 100644
--- a/hphp/runtime/base/tv_arith.cpp
+++ b/hphp/runtime/base/tv_arith.cpp
@@ -239,7 +239,6 @@ struct MulEq {
   }
 };
 
-
 template<class SzOp, class BitOp>
 StringData* stringBitOp(BitOp bop, SzOp sop, StringData* s1, StringData* s2) {
   auto const s1Size = s1->size();
@@ -489,6 +488,38 @@ void cellDec(Cell& cell) {
   cellIncDecOp(Dec(), cell);
 }
 
+void cellBitNot(Cell& cell) {
+  assert(cellIsPlausible(&cell));
+
+  switch (cell.m_type) {
+  case KindOfInt64:
+    cell.m_data.num = ~cell.m_data.num;
+    break;
+  case KindOfDouble:
+    cell.m_type     = KindOfInt64;
+    cell.m_data.num = ~toInt64(cell.m_data.dbl);
+    break;
+
+  case KindOfString:
+    if (cell.m_data.pstr->getCount() > 1) {
+    case KindOfStaticString:
+      auto const newSd = NEW(StringData)(
+        cell.m_data.pstr->slice(),
+        CopyString
+      );
+      newSd->incRefCount();
+      cell.m_data.pstr->decRefCount(); // can't go to zero
+      cell.m_data.pstr = newSd;
+      cell.m_type = KindOfString;
+    }
+    cell.m_data.pstr->negate();
+    break;
+
+  default:
+    raise_error("Unsupported operand type for ~");
+  }
+}
+
 //////////////////////////////////////////////////////////////////////
 
 }
diff --git a/hphp/runtime/base/tv_arith.h b/hphp/runtime/base/tv_arith.h
index 625ff36dc..8e3cf252b 100644
--- a/hphp/runtime/base/tv_arith.h
+++ b/hphp/runtime/base/tv_arith.h
@@ -112,6 +112,8 @@ void cellBitAndEq(Cell& c1, Cell);
 void cellBitOrEq(Cell& c1, Cell);
 void cellBitXorEq(Cell& c1, Cell);
 
+//////////////////////////////////////////////////////////////////////
+
 /*
  * PHP operator ++ and --.
  *
@@ -121,6 +123,15 @@ void cellBitXorEq(Cell& c1, Cell);
 void cellInc(Cell&);
 void cellDec(Cell&);
 
+
+/*
+ * PHP unary operator ~.
+ *
+ * Mutates the argument in place, with the effects of php's unary
+ * bitwise not operator.
+ */
+void cellBitNot(Cell&);
+
 //////////////////////////////////////////////////////////////////////
 
 }
diff --git a/hphp/runtime/base/type_string.cpp b/hphp/runtime/base/type_string.cpp
index 9a01e1615..ecf99e8b1 100644
--- a/hphp/runtime/base/type_string.cpp
+++ b/hphp/runtime/base/type_string.cpp
@@ -396,12 +396,6 @@ String operator+(const String & lhs, const String & rhs) {
   return NEW(StringData)(lhs.slice(), rhs.slice());
 }
 
-String String::operator~() const {
-  String ret(NEW(StringData)(slice(), CopyString));
-  ret->negate();
-  return ret;
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 // conversions
 
diff --git a/hphp/runtime/base/type_string.h b/hphp/runtime/base/type_string.h
index 2cdb98c3a..290106200 100644
--- a/hphp/runtime/base/type_string.h
+++ b/hphp/runtime/base/type_string.h
@@ -318,7 +318,7 @@ public:
   String &operator |= (CStrRef v) = delete;
   String &operator &= (CStrRef v) = delete;
   String &operator ^= (CStrRef v) = delete;
-  String  operator ~  () const;
+  String  operator ~  () const = delete;
   explicit operator std::string () const {
     return std::string(c_str(), size());
   }
diff --git a/hphp/runtime/base/type_variant.cpp b/hphp/runtime/base/type_variant.cpp
index 3cf643335..f0b871197 100644
--- a/hphp/runtime/base/type_variant.cpp
+++ b/hphp/runtime/base/type_variant.cpp
@@ -522,25 +522,6 @@ inline DataType Variant::convertToNumeric(int64_t *lval, double *dval) const {
   return s->isNumericWithVal(*lval, *dval, 1);
 }
 
-///////////////////////////////////////////////////////////////////////////////
-// bitwise
-
-Variant Variant::bitNot() const {
-  auto const cell = asCell();
-  switch (cell->m_type) {
-  case KindOfInt64:
-    return ~cell->m_data.num;
-  case KindOfDouble:
-    return ~toInt64(cell->m_data.dbl);
-  case KindOfStaticString:
-  case KindOfString:
-    return ~String(cell->m_data.pstr);
-  default:
-    break;
-  }
-  throw InvalidOperandException("only numerics and strings can be negated");
-}
-
 ///////////////////////////////////////////////////////////////////////////////
 // iterator functions
 
diff --git a/hphp/runtime/base/type_variant.h b/hphp/runtime/base/type_variant.h
index 01498a98f..37b7d8b49 100644
--- a/hphp/runtime/base/type_variant.h
+++ b/hphp/runtime/base/type_variant.h
@@ -590,10 +590,6 @@ class Variant : private TypedValue {
   Variant &operator -- () = delete;
   Variant  operator -- (int) = delete;
 
-  // Return the result of applying the php bitwise not operator to
-  // this value.
-  Variant bitNot() const;
-
   /**
    * Iterator functions. See array_iterator.h for end() and next().
    */
diff --git a/hphp/runtime/vm/bytecode.cpp b/hphp/runtime/vm/bytecode.cpp
index c3fbc451c..48bca008f 100644
--- a/hphp/runtime/vm/bytecode.cpp
+++ b/hphp/runtime/vm/bytecode.cpp
@@ -3768,17 +3768,7 @@ inline void OPTBLD_INLINE VMExecutionContext::iopShr(PC& pc) {
 
 inline void OPTBLD_INLINE VMExecutionContext::iopBitNot(PC& pc) {
   NEXT();
-  Cell* c1 = m_stack.topC();
-  if (LIKELY(c1->m_type == KindOfInt64)) {
-    c1->m_data.num = ~c1->m_data.num;
-  } else if (c1->m_type == KindOfDouble) {
-    c1->m_type = KindOfInt64;
-    c1->m_data.num = ~int64_t(c1->m_data.dbl);
-  } else if (IS_STRING_TYPE(c1->m_type)) {
-    cellAsVariant(*c1) = cellAsVariant(*c1).bitNot();
-  } else {
-    raise_error("Unsupported operand type for ~");
-  }
+  cellBitNot(*m_stack.topC());
 }
 
 inline void OPTBLD_INLINE VMExecutionContext::iopCastBool(PC& pc) {