diff --git a/frontend/src/app/plugins/text.cljs b/frontend/src/app/plugins/text.cljs
index 26e13b1039..597833619b 100644
--- a/frontend/src/app/plugins/text.cljs
+++ b/frontend/src/app/plugins/text.cljs
@@ -33,7 +33,7 @@
 
 (def ^:private font-size-re #"^\d*\.?\d*$")
 (def ^:private line-height-re #"^\d*\.?\d*$")
-(def ^:private letter-spacing-re #"^\d*\.?\d*$")
+(def ^:private letter-spacing-re #"^-?\d*\.?\d*$")
 (def ^:private text-transform-re #"uppercase|capitalize|lowercase|none")
 (def ^:private text-decoration-re #"underline|line-through|none")
 (def ^:private text-direction-re #"ltr|rtl")
diff --git a/frontend/test/frontend_tests/plugins/text_test.cljs b/frontend/test/frontend_tests/plugins/text_test.cljs
new file mode 100644
index 0000000000..edcfbf853d
--- /dev/null
+++ b/frontend/test/frontend_tests/plugins/text_test.cljs
@@ -0,0 +1,37 @@
+;; This Source Code Form is subject to the terms of the Mozilla Public
+;; License, v. 2.0. If a copy of the MPL was not distributed with this
+;; file, You can obtain one at http://mozilla.org/MPL/2.0/.
+;;
+;; Copyright (c) KALEIDOS INC
+
+(ns frontend-tests.plugins.text-test
+  (:require
+   [app.plugins.text :as plugins.text]
+   [cljs.test :as t :include-macros true]))
+
+;; Regression coverage for issue #9780.
+;;
+;; `letterSpacing` accepts negative tracking in the product UI (-200..200,
+;; see typography.cljs), but the plugin validator regex rejected any leading
+;; minus, so negative values were refused. `letter-spacing-re` is the shared
+;; predicate behind both the shape- and range-level setters; pin its
+;; accept/reject contract here.
+
+(def ^:private letter-spacing-re @#'plugins.text/letter-spacing-re)
+
+(defn- valid? [s] (boolean (re-matches letter-spacing-re s)))
+
+(t/deftest letter-spacing-re-accepts-negative-values
+  (t/is (valid? "-0.56"))
+  (t/is (valid? "-12"))
+  (t/is (valid? "-200")))
+
+(t/deftest letter-spacing-re-accepts-non-negative-values
+  (t/is (valid? "0"))
+  (t/is (valid? "12"))
+  (t/is (valid? "1.5")))
+
+(t/deftest letter-spacing-re-rejects-non-numeric
+  (t/is (not (valid? "abc")))
+  (t/is (not (valid? "1-2")))
+  (t/is (not (valid? "--1"))))
diff --git a/frontend/test/frontend_tests/runner.cljs b/frontend/test/frontend_tests/runner.cljs
index b3b16a2079..154dd95ad9 100644
--- a/frontend/test/frontend_tests/runner.cljs
+++ b/frontend/test/frontend_tests/runner.cljs
@@ -33,6 +33,7 @@
    [frontend-tests.plugins.page-active-validation-test]
    [frontend-tests.plugins.page-test]
    [frontend-tests.plugins.parser-test]
+   [frontend-tests.plugins.text-test]
    [frontend-tests.plugins.tokens-test]
    [frontend-tests.plugins.utils-test]
    [frontend-tests.render-wasm.process-objects-test]
@@ -89,6 +90,7 @@
     frontend-tests.plugins.format-test
     frontend-tests.plugins.page-test
     frontend-tests.plugins.parser-test
+    frontend-tests.plugins.text-test
     frontend-tests.plugins.tokens-test
     frontend-tests.plugins.utils-test
     frontend-tests.svg-fills-test