diff --git a/lib/liquid/expression.rb b/lib/liquid/expression.rb
index 0a569e99..0d8a4471 100644
--- a/lib/liquid/expression.rb
+++ b/lib/liquid/expression.rb
@@ -109,12 +109,6 @@ module Liquid
       end
 
       def parse_number(markup, ss)
-        ss.string = markup
-        # the first byte must be a digit, a period, or  a dash
-        byte = ss.scan_byte
-
-        return false if byte != DASH && byte != DOT && (byte < ZERO || byte > NINE)
-
         # check if the markup is simple integer or float
         case markup
         when INTEGER_REGEX
@@ -123,6 +117,12 @@ module Liquid
           return markup.to_f
         end
 
+        ss.string = markup
+        # the first byte must be a digit, a period, or  a dash
+        byte = ss.scan_byte
+
+        return false if byte != DASH && byte != DOT && (byte < ZERO || byte > NINE)
+
         # The markup could be a float with multiple dots
         first_dot_pos = nil
         num_end_pos = nil