diff --git a/layout/style/test/property_database.js b/layout/style/test/property_database.js
index 1f7b98f01180..d4b210973e1c 100644
--- a/layout/style/test/property_database.js
+++ b/layout/style/test/property_database.js
@@ -6754,6 +6754,8 @@ var gCSSProperties = {
domProp: "opacity",
inherited: false,
type: CSS_TYPE_LONGHAND,
+ applies_to_first_letter: true,
+ applies_to_first_line: true,
applies_to_placeholder: true,
applies_to_cue: true,
initial_values: [
diff --git a/servo/components/style/properties/data.py b/servo/components/style/properties/data.py
index 8e6cdd79a1b6..9ab3a40ca668 100644
--- a/servo/components/style/properties/data.py
+++ b/servo/components/style/properties/data.py
@@ -688,6 +688,7 @@ class PropertyRestrictions:
def first_letter(data):
props = set([
"color",
+ "opacity",
"float",
"initial-letter",
@@ -722,6 +723,7 @@ class PropertyRestrictions:
props = set([
# Per spec.
"color",
+ "opacity",
# Kinda like css-fonts?
"-moz-osx-font-smoothing",
diff --git a/testing/web-platform/meta/css/css-pseudo/first-letter-allowed-properties.html.ini b/testing/web-platform/meta/css/css-pseudo/first-letter-allowed-properties.html.ini
index da26e4abbd57..310f12b82203 100644
--- a/testing/web-platform/meta/css/css-pseudo/first-letter-allowed-properties.html.ini
+++ b/testing/web-platform/meta/css/css-pseudo/first-letter-allowed-properties.html.ini
@@ -18,9 +18,6 @@
[margin should be applied to first-letter pseudo elements.]
expected: FAIL
- [opacity should be applied to first-letter pseudo elements.]
- expected: FAIL
-
[padding should be applied to first-letter pseudo elements.]
expected: FAIL
diff --git a/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001-not-ref.html b/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001-not-ref.html
new file mode 100644
index 000000000000..d1844499baa4
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001-not-ref.html
@@ -0,0 +1,10 @@
+
+
+
+Reference mismatch: ::first-letter supports opacity.
+
+
+
+ First
+
+
diff --git a/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001-ref.html b/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001-ref.html
new file mode 100644
index 000000000000..37e4dd5a2c91
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001-ref.html
@@ -0,0 +1,16 @@
+
+
+
+Reference: ::first-letter supports opacity.
+
+
+
+
+
+ First
+
+
diff --git a/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001.html b/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001.html
new file mode 100644
index 000000000000..0a867e541aeb
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/first-letter-opacity-001.html
@@ -0,0 +1,17 @@
+
+
+
+CSS Test: ::first-letter supports opacity.
+
+
+
+
+
+
+ First
+
+
diff --git a/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001-not-ref.html b/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001-not-ref.html
new file mode 100644
index 000000000000..d020842a24b2
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001-not-ref.html
@@ -0,0 +1,10 @@
+
+
+
+Reference mismatch: ::first-line supports opacity.
+
+
+
+ First
Second
+
+
diff --git a/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001-ref.html b/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001-ref.html
new file mode 100644
index 000000000000..b4f4ddc185fc
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001-ref.html
@@ -0,0 +1,16 @@
+
+
+
+Reference: ::first-line supports opacity.
+
+
+
+
+
+ First
Second
+
+
diff --git a/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001.html b/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001.html
new file mode 100644
index 000000000000..83f90824b8ab
--- /dev/null
+++ b/testing/web-platform/tests/css/css-pseudo/first-line-opacity-001.html
@@ -0,0 +1,17 @@
+
+
+
+CSS Test: ::first-line supports opacity.
+
+
+
+
+
+
+ First
Second
+
+