diff --git a/src/css/Properties.js b/src/css/Properties.js
index 4d792438..37312d3d 100644
--- a/src/css/Properties.js
+++ b/src/css/Properties.js
@@ -14,6 +14,7 @@ var Properties = {
     "animation-delay"               : { multi: "<time>", comma: true },
     "animation-direction"           : { multi: "normal | alternate", comma: true },
     "animation-duration"            : { multi: "<time>", comma: true },
+    "animation-fill-mode"           : { multi: "none | forwards | backwards | both", comma: true },
     "animation-iteration-count"     : { multi: "<number> | infinite", comma: true },
     "animation-name"                : { multi: "none | <ident>", comma: true },
     "animation-play-state"          : { multi: "running | paused", comma: true },
@@ -37,6 +38,7 @@ var Properties = {
     "-webkit-animation-delay"               : { multi: "<time>", comma: true },
     "-webkit-animation-direction"           : { multi: "normal | alternate", comma: true },
     "-webkit-animation-duration"            : { multi: "<time>", comma: true },
+    "-webkit-animation-fill-mode"           : { multi: "none | forwards | backwards | both", comma: true },
     "-webkit-animation-iteration-count"     : { multi: "<number> | infinite", comma: true },
     "-webkit-animation-name"                : { multi: "none | <ident>", comma: true },
     "-webkit-animation-play-state"          : { multi: "running | paused", comma: true },
diff --git a/tests/css/Validation.js b/tests/css/Validation.js
index 1f051bef..0895326f 100644
--- a/tests/css/Validation.js
+++ b/tests/css/Validation.js
@@ -61,6 +61,22 @@
 
     var suite = new YUITest.TestSuite("Validation Tests");
 
+    suite.add(new ValidationTestCase({
+        property: "animation-fill-mode",
+
+        valid: [
+            "none",
+            "forwards",
+            "backwards",
+            "both",
+            "none, forwards"
+        ],
+
+        invalid: {
+            "1px" : "Expected (none | forwards | backwards | both) but found '1px'."
+        }
+    }));
+
     suite.add(new ValidationTestCase({
         property: "animation-name",