--- a/libinterp/parse-tree/lex.ll
+++ b/libinterp/parse-tree/lex.ll
@@ -103,8 +103,7 @@
 #undef YY_INPUT
 #endif
 #define YY_INPUT(buf, result, max_size) \
-  if ((result = octave_read (buf, max_size)) < 0) \
-    YY_FATAL_ERROR ("octave_read () in flex scanner failed");
+  result = octave_read (buf, max_size)
 
 // Try to avoid crashing out completely on fatal scanner errors.
 // The call to yy_fatal_error should never happen, but it avoids a
@@ -322,6 +321,7 @@
 static void scan_for_comments (const char *);
 static yum_yum eat_whitespace (void);
 static yum_yum eat_continuation (void);
+static int octave_read (char *buf, unsigned int max_size);
 static void maybe_warn_separator_insert (char sep);
 static void gripe_single_quote_string (void);
 static void gripe_matlab_incompatible (const std::string& msg);
@@ -3550,6 +3550,70 @@
   BEGIN (FUNCTION_FILE_BEGIN);
 }
 
+static int
+octave_read (char *buf, unsigned max_size)
+{
+  static const char * const eol = "\n";
+  static std::string input_buf;
+  static const char *pos = 0;
+  static size_t chars_left = 0;
+  static bool eof = false;
+
+  int status = 0;
+
+  if (chars_left == 0)
+    {
+      pos = 0;
+
+      input_buf = get_user_input (eof);
+
+      chars_left = input_buf.length ();
+
+      pos = input_buf.c_str ();
+    }
+
+  if (chars_left > 0)
+    {
+      size_t len = max_size > chars_left ? chars_left : max_size;
+      assert (len > 0);
+
+      memcpy (buf, pos, len);
+
+      chars_left -= len;
+      pos += len;
+
+      // Make sure input ends with a new line character.
+      if (chars_left == 0 && buf[len-1] != '\n')
+        {
+          if (len < max_size)
+            {
+              // There is enough room to plug the newline character in
+              // the buffer.
+              buf[len++] = '\n';
+            }
+          else
+            {
+              // There isn't enough room to plug the newline character
+              // in the buffer so make sure it is returned on the next
+              // octave_read call.
+              pos = eol;
+              chars_left = 1;
+            }
+        }
+
+      status = len;
+    }
+  else
+    {
+      status = YY_NULL;
+
+      if (! eof)
+        YY_FATAL_ERROR ("octave_read () in flex scanner failed");
+    }
+
+  return status;
+}
+
 static void
 maybe_warn_separator_insert (char sep)
 {