diff --git a/lisp/progmodes/ruby-mode.el b/lisp/progmodes/ruby-mode.el
index 5c34ddc562b..b2d833fa2b0 100644
--- a/lisp/progmodes/ruby-mode.el
+++ b/lisp/progmodes/ruby-mode.el
@@ -2125,7 +2125,7 @@ ruby-find-library-file
                    "or" "not" "&&" "||"))
      ;; Method name from the list.
      "\\|\\_<"
-     (regexp-opt ruby-syntax-methods-before-regexp)
+     (regexp-opt ruby-syntax-methods-before-regexp t)
      "\\)\\s *")
     "Regexp to match text that can be followed by a regular expression."))
 
@@ -2183,14 +2183,18 @@ ruby-syntax-propertize
         (when (save-excursion
                 (forward-char -1)
                 (cl-evenp (skip-chars-backward "\\\\")))
-          (let ((state (save-excursion (syntax-ppss (match-beginning 1)))))
+          (let ((state (save-excursion (syntax-ppss (match-beginning 1))))
+                space-after-slash)
             (when (or
                    ;; Beginning of a regexp.
                    (and (null (nth 8 state))
                         (save-excursion
+                          (setq space-after-slash (eql (char-after) ?\s))
                           (forward-char -1)
                           (looking-back ruby-syntax-before-regexp-re
-                                        (line-beginning-position))))
+                                        (line-beginning-position)))
+                        (or (not space-after-slash)
+                            (not (match-beginning 2))))
                    ;; End of regexp.  We don't match the whole
                    ;; regexp at once because it can have
                    ;; string interpolation inside, or span