diff --git a/lisp/progmodes/flymake.el b/lisp/progmodes/flymake.el
index 9dda53713f5..d3bbb98a93e 100644
--- a/lisp/progmodes/flymake.el
+++ b/lisp/progmodes/flymake.el
@@ -748,34 +748,41 @@ flymake--severity
   (flymake--lookup-type-property type 'severity
                                  (warning-numeric-level :error)))
 
-(defun flymake--indicator-overlay-spec (indicator)
+(defun flymake--indicator-overlay-spec (type)
   "Return INDICATOR as propertized string to use in error indicators."
-  (let* ((value (if (symbolp indicator)
+  (let* ((indicator (flymake--lookup-type-property
+                     type
+                     (cond ((eq flymake-indicator-type 'fringes)
+                            'flymake-bitmap)
+                           ((eq flymake-indicator-type 'margins)
+                            'flymake-margin-string))
+                     (alist-get 'bitmap (alist-get type ; backward compat
+                                                   flymake-diagnostic-types-alist))))
+         (value (if (symbolp indicator)
                     (symbol-value indicator)
                   indicator))
-         (indicator-car (if (listp value)
-                            (car value)
-                          value))
-         (indicator-cdr (if (listp value)
-                            (cdr value))))
+         (valuelist (if (listp value)
+                        value
+                      (list value)))
+         (indicator-car (car valuelist)))
+
     (cond
      ((and (symbolp indicator-car)
            flymake-fringe-indicator-position)
       (propertize "!" 'display
-                  (cons flymake-fringe-indicator-position
-                        (if (listp value)
-                            value
-                          (list value)))))
+                  (cons flymake-fringe-indicator-position valuelist)))
      ((and (stringp indicator-car)
            flymake-margin-indicator-position)
       (propertize "!"
                   'display
                   `((margin ,flymake-margin-indicator-position)
-                    ,(propertize
-                      indicator-car
-                      'face
-                      `(:inherit (,indicator-cdr
-                                  default)))))))))
+                    ,(propertize indicator-car
+                                 'face `(:inherit (,(cdr valuelist) default))
+                                 'mouse-face 'highlight
+                                 'help-echo "Open Flymake diagnostics"
+                                 'keymap `,(define-keymap
+                                             (format "<%s> <mouse-1>" flymake-margin-indicator-position)
+                                             #'flymake-show-buffer-diagnostics))))))))
 
 (defun flymake--resize-margins (&optional orig-width)
   "Resize current window margins according to `flymake-margin-indicator-position'.
@@ -941,16 +948,7 @@ flymake--highlight-line
                   (overlay-put ov prop (flymake--lookup-type-property
                                         type prop value)))))
       (default-maybe 'face 'flymake-error)
-      (default-maybe 'before-string
-        (flymake--indicator-overlay-spec
-         (flymake--lookup-type-property
-          type
-          (cond ((eq flymake-indicator-type 'fringes)
-                 'flymake-bitmap)
-                ((eq flymake-indicator-type 'margins)
-                 'flymake-margin-string))
-          (alist-get 'bitmap (alist-get type ; backward compat
-                                        flymake-diagnostic-types-alist)))))
+      (default-maybe 'before-string (flymake--indicator-overlay-spec type))
       ;; (default-maybe 'after-string
       ;;                (flymake--diag-text diagnostic))
       (default-maybe 'help-echo
@@ -1369,11 +1367,7 @@ flymake-start
                   nil)))
              (flymake--import-foreign-diagnostics))))))
 
-(defvar flymake-mode-map
-  (let ((map (make-sparse-keymap)))
-    (define-key map `[,flymake-fringe-indicator-position mouse-1]
-                #'flymake-show-buffer-diagnostics)
-    map)
+(defvar flymake-mode-map (make-sparse-keymap)
   "Keymap for `flymake-mode'.")
 
 ;;;###autoload