diff --git a/src/lib.rs b/src/lib.rs
index 2005a6da..f0547df0 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -29411,6 +29411,76 @@ mod tests {
     assert_eq!(property, Property::ColorInterpolation(svg::ColorInterpolation::SRGB));
   }
 
+  #[test]
+  fn test_mask_image_prefix_duplicates() {
+    let targets = Browsers {
+      chrome: Some(90 << 16),
+      ..Browsers::default()
+    };
+
+    for (source, expected) in [
+      (
+        ".foo { -webkit-mask-image: var(--image); mask-image: var(--image) }",
+        indoc! { r#"
+          .foo {
+            -webkit-mask-image: var(--image);
+            mask-image: var(--image);
+          }
+        "#},
+      ),
+      (
+        ".foo { mask-image: var(--first); mask-image: var(--second) }",
+        indoc! { r#"
+          .foo {
+            -webkit-mask-image: var(--first);
+            mask-image: var(--first);
+            -webkit-mask-image: var(--second);
+            mask-image: var(--second);
+          }
+        "#},
+      ),
+      (
+        ".foo { mask-image: var(--image); mask-position: center; -webkit-mask-image: var(--image) }",
+        indoc! { r#"
+          .foo {
+            -webkit-mask-image: var(--image);
+            mask-image: var(--image);
+            -webkit-mask-position: center;
+            mask-position: center;
+            -webkit-mask-image: var(--image);
+          }
+        "#},
+      ),
+      (
+        ".foo { mask-image: var(--image) !important; -webkit-mask-image: var(--image) }",
+        indoc! { r#"
+          .foo {
+            -webkit-mask-image: var(--image);
+            -webkit-mask-image: var(--image) !important;
+            mask-image: var(--image) !important;
+          }
+        "#},
+      ),
+    ] {
+      prefix_test(source, expected, targets);
+      prefix_test(expected, expected, targets);
+    }
+
+    prefix_test(
+      ".foo { -webkit-mask-image: var(--image); mask-image: var(--image) }",
+      indoc! { r#"
+        .foo {
+          -webkit-mask-image: var(--image);
+          mask-image: var(--image);
+        }
+      "#},
+      Browsers {
+        chrome: Some(130 << 16),
+        ..Browsers::default()
+      },
+    );
+  }
+
   #[test]
   fn test_filter() {
     property_range_test(
diff --git a/src/properties/masking.rs b/src/properties/masking.rs
index 784e6b11..e0ae9132 100644
--- a/src/properties/masking.rs
+++ b/src/properties/masking.rs
@@ -704,7 +704,20 @@ impl<'i> PropertyHandler<'i> for MaskHandler<'i> {
         self
           .flushed_properties
           .insert(MaskProperty::try_from(&val.property_id).unwrap());
-        dest.push(Property::Unparsed(unparsed));
+        let mut merged = false;
+        if let (PropertyId::MaskImage(prefix), Some(Property::Unparsed(previous))) =
+          (&unparsed.property_id, dest.last_mut())
+        {
+          if let PropertyId::MaskImage(previous_prefix) = &mut previous.property_id {
+            if previous.value == unparsed.value {
+              *previous_prefix |= *prefix;
+              merged = true;
+            }
+          }
+        }
+        if !merged {
+          dest.push(Property::Unparsed(unparsed));
+        }
       }
       Property::MaskBorderSource(val) => property!(border_source, val, &VendorPrefix::None),
       Property::WebKitMaskBoxImageSource(val, _) => property!(border_source, val, &VendorPrefix::WebKit),