diff --git a/css/properties.json b/css/properties.json
index 3662ee8e..160f325a 100644
--- a/css/properties.json
+++ b/css/properties.json
@@ -4766,7 +4766,7 @@
     "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/fill"
   },
   "fill-opacity": {
-    "syntax": "<alpha-value>",
+    "syntax": "<'opacity'>",
     "media": "visual",
     "inherited": true,
     "animationType": "byComputedValueType",
@@ -7581,7 +7581,7 @@
     "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/offset-rotate"
   },
   "opacity": {
-    "syntax": "<alpha-value>",
+    "syntax": "<opacity-value>",
     "media": "visual",
     "inherited": false,
     "animationType": "byComputedValueType",
@@ -9398,7 +9398,7 @@
     "mdn_url": "https://developer.mozilla.org/docs/Web/CSS/scroll-timeline-name"
   },
   "shape-image-threshold": {
-    "syntax": "<alpha-value>",
+    "syntax": "<opacity-value>",
     "media": "visual",
     "inherited": false,
     "animationType": "number",
diff --git a/css/syntaxes.json b/css/syntaxes.json
index 4a0ce22e..1fd145b5 100644
--- a/css/syntaxes.json
+++ b/css/syntaxes.json
@@ -578,6 +578,9 @@
   "opacity()": {
     "syntax": "opacity( [ <number-percentage> ] )"
   },
+  "opacity-value": {
+    "syntax": "<number> | <percentage>"
+  },
   "overflow-position": {
     "syntax": "unsafe | safe"
   },
diff --git a/css/syntaxes.md b/css/syntaxes.md
index dd7510cf..58f64118 100644
--- a/css/syntaxes.md
+++ b/css/syntaxes.md
@@ -40,7 +40,7 @@ Or, syntaxes might reference other syntaxes that are also defined in syntaxes.js
   "syntax": "<length> | <percentage>"
 },
 "shape-radius": {
-    "syntax": "<length-percentage> | closest-side | farthest-side"
+  "syntax": "<length-percentage> | closest-side | farthest-side"
 },
 ```