diff --git a/src/ralph/models/edx/converters/xapi/video.py b/src/ralph/models/edx/converters/xapi/video.py
index 822d97cd8..9ab305b17 100644
--- a/src/ralph/models/edx/converters/xapi/video.py
+++ b/src/ralph/models/edx/converters/xapi/video.py
@@ -10,6 +10,7 @@
 )
 from ralph.models.xapi.constants import LANG_EN_US_DISPLAY
 from ralph.models.xapi.video.constants import (
+    VIDEO_EXTENSION_LENGTH,
     VIDEO_EXTENSION_TIME,
     VIDEO_EXTENSION_TIME_FROM,
     VIDEO_EXTENSION_TIME_TO,
@@ -58,6 +59,20 @@ class UILoadVideoToVideoInitialized(VideoBaseXapiConverter):
     __src__ = UILoadVideo
     __dest__ = VideoInitialized
 
+    def _get_conversion_items(self):
+        """Returns a set of ConversionItems used for conversion."""
+
+        conversion_items = super()._get_conversion_items()
+        return conversion_items.union(
+            {
+                ConversionItem(
+                    "context__extensions__" + VIDEO_EXTENSION_LENGTH,
+                    None,
+                    lambda _: 1,
+                ),
+            },
+        )
+
 
 class UIPlayVideoToVideoPlayed(VideoBaseXapiConverter):
     """Converts a common edX `play_video` event to xAPI."""
diff --git a/src/ralph/models/xapi/video/fields/contexts.py b/src/ralph/models/xapi/video/fields/contexts.py
index 4763982e3..6324dff0e 100644
--- a/src/ralph/models/xapi/video/fields/contexts.py
+++ b/src/ralph/models/xapi/video/fields/contexts.py
@@ -83,7 +83,7 @@ class VideoInitializedContextExtensionsField(VideoContextExtensionsField):
             consumed to trigger a completion.
     """
 
-    length: float = Field(alias=VIDEO_EXTENSION_LENGTH, default_factory=float)
+    length: float = Field(alias=VIDEO_EXTENSION_LENGTH)
     ccSubtitleEnabled: Optional[bool] = Field(alias=VIDEO_EXTENSION_CC_SUBTITLE_ENABLED)
     ccSubtitleLanguage: Optional[str] = Field(alias=VIDEO_EXTENSION_CC_SUBTITLE_LANG)
     frameRate: Optional[float] = Field(alias=VIDEO_EXTENSION_FRAME_RATE)
diff --git a/tests/fixtures/hypothesis_configuration.py b/tests/fixtures/hypothesis_configuration.py
index 7a5ed787b..0ef784f3b 100644
--- a/tests/fixtures/hypothesis_configuration.py
+++ b/tests/fixtures/hypothesis_configuration.py
@@ -31,6 +31,7 @@ def custom_resolve_json(cls):
 settings.load_profile("development")
 
 st.register_type_strategy(str, st.text(min_size=1))
+st.register_type_strategy(float, st.floats(min_value=0.0))
 st.register_type_strategy(StrictStr, st.text(min_size=1))
 st.register_type_strategy(AnyUrl, provisional.urls())
 st.register_type_strategy(AnyHttpUrl, provisional.urls())