diff --git a/Tests/LibWeb/Text/expected/WebAnimations/misc/invalid-values.txt b/Tests/LibWeb/Text/expected/WebAnimations/misc/invalid-values.txt
index 49cbed31b5a..27868db8f39 100644
--- a/Tests/LibWeb/Text/expected/WebAnimations/misc/invalid-values.txt
+++ b/Tests/LibWeb/Text/expected/WebAnimations/misc/invalid-values.txt
@@ -5,6 +5,9 @@ KeyframeEffect with infinite endDelay value: threw an exception
 KeyframeEffect with NaN endDelay value: threw an exception
 KeyframeEffect with NaN iterations: threw an exception
 KeyframeEffect with non-"auto" string duration: threw an exception
+KeyframeEffect with non-numeric offset: threw an exception
+KeyframeEffect with invalid numeric offset: threw an exception
+
 KeyframeEffect with infinite options value: did not throw an exception
 KeyframeEffect with finite options value: did not throw an exception
 KeyframeEffect with infinite iterations: did not throw an exception
diff --git a/Tests/LibWeb/Text/input/WebAnimations/misc/invalid-values.html b/Tests/LibWeb/Text/input/WebAnimations/misc/invalid-values.html
index bcd274f1a3d..a8d909c75ad 100644
--- a/Tests/LibWeb/Text/input/WebAnimations/misc/invalid-values.html
+++ b/Tests/LibWeb/Text/input/WebAnimations/misc/invalid-values.html
@@ -19,6 +19,10 @@
         checkException('KeyframeEffect with NaN endDelay value', () => new KeyframeEffect(null, null, { endDelay: NaN }));
         checkException('KeyframeEffect with NaN iterations', () => new KeyframeEffect(null, null, { iterations: NaN }));
         checkException('KeyframeEffect with non-"auto" string duration', () => new KeyframeEffect(null, null, { duration: 'abc' }))
+        checkException('KeyframeEffect with non-numeric offset', () => new KeyframeEffect(null, [{ offset: 'abc' }], {}));
+        checkException('KeyframeEffect with invalid numeric offset', () => new KeyframeEffect(null, [{ offset: -1 }], {}));
+
+        println('');
 
         // Test valid values
         checkException('KeyframeEffect with infinite options value', () => new KeyframeEffect(null, null, Infinity));
diff --git a/Userland/Libraries/LibWeb/Animations/KeyframeEffect.cpp b/Userland/Libraries/LibWeb/Animations/KeyframeEffect.cpp
index 579cc0e1db5..822a2778deb 100644
--- a/Userland/Libraries/LibWeb/Animations/KeyframeEffect.cpp
+++ b/Userland/Libraries/LibWeb/Animations/KeyframeEffect.cpp
@@ -57,10 +57,13 @@ static WebIDL::ExceptionOr<KeyframeType<AL>> process_a_keyframe_like_object(JS::
 {
     auto& vm = realm.vm();
 
-    Function<WebIDL::ExceptionOr<Optional<double>>(JS::Value)> to_nullable_double = [&vm](JS::Value value) -> WebIDL::ExceptionOr<Optional<double>> {
+    Function<WebIDL::ExceptionOr<Optional<double>>(JS::Value)> to_offset = [&vm](JS::Value value) -> WebIDL::ExceptionOr<Optional<double>> {
         if (value.is_undefined())
             return Optional<double> {};
-        return TRY(value.to_double(vm));
+        auto double_value = TRY(value.to_double(vm));
+        if (isnan(double_value) || isinf(double_value))
+            return WebIDL::SimpleException { WebIDL::SimpleExceptionType::TypeError, MUST(String::formatted("Invalid offset value: {}", TRY(value.to_string(vm)))) };
+        return double_value;
     };
 
     Function<WebIDL::ExceptionOr<String>(JS::Value)> to_string = [&vm](JS::Value value) -> WebIDL::ExceptionOr<String> {
@@ -102,7 +105,7 @@ static WebIDL::ExceptionOr<KeyframeType<AL>> process_a_keyframe_like_object(JS::
         composite = JS::PrimitiveString::create(vm, "auto"_string);
 
     if constexpr (AL == AllowLists::Yes) {
-        keyframe_output.offset = TRY(convert_value_to_maybe_list(realm, offset, to_nullable_double));
+        keyframe_output.offset = TRY(convert_value_to_maybe_list(realm, offset, to_offset));
         keyframe_output.composite = TRY(convert_value_to_maybe_list(realm, composite, to_composite_operation));
 
         auto easing_maybe_list = TRY(convert_value_to_maybe_list(realm, easing, to_string));
@@ -117,7 +120,7 @@ static WebIDL::ExceptionOr<KeyframeType<AL>> process_a_keyframe_like_object(JS::
                 keyframe_output.easing = move(easing_values);
             });
     } else {
-        keyframe_output.offset = TRY(to_nullable_double(offset));
+        keyframe_output.offset = TRY(to_offset(offset));
         keyframe_output.easing = TRY(to_string(easing));
         keyframe_output.composite = TRY(to_composite_operation(composite));
     }