diff --git a/src/Lexer.cpp b/src/Lexer.cpp
index 992eb7a1c..338f12b5e 100644
--- a/src/Lexer.cpp
+++ b/src/Lexer.cpp
@@ -294,6 +294,22 @@ bool Lexer::isBoundary (int left, int right)
   return false;
 }
 
+////////////////////////////////////////////////////////////////////////////////
+bool Lexer::isHardBoundary (int left, int right)
+{
+  // EOS
+  if (right == '\0')                                               return true;
+
+  // FILTER operators that don't need to be surrounded by whitespace.
+  if (left == '(' ||
+      left == ')' ||
+      right == '(' ||
+      right == ')')
+    return true;
+
+  return false;
+}
+
 ////////////////////////////////////////////////////////////////////////////////
 bool Lexer::isPunctuation (int c)
 {
@@ -1230,6 +1246,11 @@ bool Lexer::readWord (
 //   abcU+0020def
 //   abc\u0020def
 //   a\tb
+//
+// Ends at:
+//   Lexer::isEOS
+//   Lexer::isWhitespace
+//   Lexer::isHardBoundary
 bool Lexer::readWord (
   const std::string& text,
   std::string::size_type& cursor,
@@ -1239,12 +1260,17 @@ bool Lexer::readWord (
 
   word = "";
   int c;
-  while ((c = text[cursor]))
+  int prev = 0;
+  while ((c = text[cursor]))  // Handles EOS.
   {
     // Unquoted word ends on white space.
     if (Lexer::isWhitespace (c))
       break;
 
+    // Parentheses mostly.
+    if (prev && Lexer::isHardBoundary (prev, c))
+      break;
+
     // Unicode U+XXXX or \uXXXX codepoint.
     else if (eos - cursor >= 6 &&
              ((text[cursor + 0] == 'U'  && text[cursor + 1] == '+') ||
@@ -1290,6 +1316,8 @@ bool Lexer::readWord (
     // Ordinary character.
     else
       word += utf8_character (utf8_next_char (text, cursor));
+
+    prev = c;
   }
 
   return word.length () > 0 ? true : false;
diff --git a/src/Lexer.h b/src/Lexer.h
index d2f04b435..7f96bda00 100644
--- a/src/Lexer.h
+++ b/src/Lexer.h
@@ -70,6 +70,7 @@ public:
   static bool isDoubleCharOperator  (int, int, int);
   static bool isTripleCharOperator  (int, int, int, int);
   static bool isBoundary            (int, int);
+  static bool isHardBoundary        (int, int);
   static bool isPunctuation         (int);
   static bool isAllDigits           (const std::string&);
   static bool isOneWord             (const std::string&);