diff --git a/tp-tests.el b/tp-tests.el
index 11008fe..26cd768 100644
--- a/tp-tests.el
+++ b/tp-tests.el
@@ -3066,7 +3066,10 @@ the source text should be used and the reactive variable should be updated."
             (should (equal (tp-at 0 'tp-text result) "2")))
           ;; Now set the variable to a different value and test again
           (setq tp-test-text-var "18")
-          ;; Redefine layer to reset resolved props
+          ;; Redefine layer to reset resolved props to the new variable value.
+          ;; This is necessary because the layer definition caches the resolved
+          ;; tp-text value, and we want to test the behavior when the variable
+          ;; already has a non-nil value at layer application time.
           (tp-define-layer 'test-init-text-layer
             :props '(face bold tp-text $tp-test-text-var))
           (let ((result (tp-set "2" 'test-init-text-layer)))
diff --git a/tp.el b/tp.el
index 114b2b9..5eebd3e 100644
--- a/tp.el
+++ b/tp.el
@@ -668,13 +668,16 @@ NEW-OBJECT is the new string object (only different for strings with tp-text)."
           ;; This ensures the reactive variable and buffer text stay in sync
           (when-let ((layer-name (plist-get props 'tp-name)))
             (when-let ((reactive-var (tp--find-tp-text-reactive-var layer-name)))
-              ;; Update the reactive variable with the current text (buffer-local)
+              ;; Update the reactive variable with the current text
+              ;; Note: Using global `set` here because the layer definition is global.
+              ;; When the variable is changed, the reactive watcher will update all
+              ;; buffers that have this layer applied.
               (set reactive-var current-text)
               ;; Also update the layer definition so future accesses see the new value
               (let ((layer-props (cdr (assoc layer-name tp-layer-alist))))
                 (when layer-props
-                  (setf (cdr (assoc layer-name tp-layer-alist))
-                        (plist-put layer-props 'tp-text current-text))))))
+                  (tp--set-layer-props layer-name
+                                       (plist-put layer-props 'tp-text current-text))))))
           (list (plist-put props 'tp-text current-text) end object)))
        ;; tp-text has a string value - replace the text in the region
        ((stringp tp-text-val)