diff --git a/include/twn_context.h b/include/twn_context.h
index 8cdb342..b312112 100644
--- a/include/twn_context.h
+++ b/include/twn_context.h
@@ -20,7 +20,6 @@ typedef struct Context {
 
     /* real time spent on one frame (in seconds) */
     /* townengine is fixed step based, so you don't have to use delta */
-    /* TODO: actually set it */
     float frame_duration;
 
     /* it is disabled by having fog_density approximately equal to zero */
diff --git a/src/twn_loop.c b/src/twn_loop.c
index ab49e36..12bacaf 100644
--- a/src/twn_loop.c
+++ b/src/twn_loop.c
@@ -532,6 +532,7 @@ static bool initialize(void) {
     ctx.desired_frametime = ctx.clocks_per_second / ctx.ticks_per_second;
     ctx.frame_accumulator = 0;
     ctx.game.frame_number = 0;
+    ctx.game.frame_duration = 1.0f / (float)ctx.ticks_per_second;
 
     /* delta time averaging */
     ctx.delta_averager_residual = 0;