diff --git a/graphics/field_effects/pics/unknown_16.png b/graphics/field_effects/pics/jump_long_grass.png
similarity index 100%
rename from graphics/field_effects/pics/unknown_16.png
rename to graphics/field_effects/pics/jump_long_grass.png
diff --git a/spritesheet_rules.mk b/spritesheet_rules.mk
index ae79719602..9fb184638a 100644
--- a/spritesheet_rules.mk
+++ b/spritesheet_rules.mk
@@ -636,7 +636,7 @@ $(FLDEFFGFXDIR)/tall_grass.4bpp: %.4bpp: %.png
 $(FLDEFFGFXDIR)/tree_disguise.4bpp: %.4bpp: %.png
 	$(GFX) $< $@ -mwidth 2 -mheight 4
 
-$(FLDEFFGFXDIR)/unknown_16.4bpp: %.4bpp: %.png
+$(FLDEFFGFXDIR)/jump_long_grass.4bpp: %.4bpp: %.png
 	$(GFX) $< $@ -mwidth 2 -mheight 2
 
 $(FLDEFFGFXDIR)/unknown_17.4bpp: %.4bpp: %.png
diff --git a/src/data/object_events/object_event_graphics.h b/src/data/object_events/object_event_graphics.h
index 81d83a8563..6ee56cc78e 100755
--- a/src/data/object_events/object_event_graphics.h
+++ b/src/data/object_events/object_event_graphics.h
@@ -305,7 +305,7 @@ const u16 gFieldEffectObjectPalette1[] = INCBIN_U16("graphics/field_effects/pale
 const u32 gFieldEffectObjectPic_GroundImpactDust[] = INCBIN_U32("graphics/field_effects/pics/ground_impact_dust.4bpp");
 const u32 gFieldEffectObjectPic_JumpTallGrass[] = INCBIN_U32("graphics/field_effects/pics/jump_tall_grass.4bpp");
 const u32 gUnusedGrass3[] = INCBIN_U32("graphics/field_effects/pics/unused_grass_3.4bpp");
-const u32 gFieldEffectObjectPic_JumpLongGrass[] = INCBIN_U32("graphics/field_effects/pics/unknown_16.4bpp");
+const u32 gFieldEffectObjectPic_JumpLongGrass[] = INCBIN_U32("graphics/field_effects/pics/jump_long_grass.4bpp");
 const u32 gFieldEffectObjectPic_Unknown17[] = INCBIN_U32("graphics/field_effects/pics/unknown_17.4bpp");
 const u32 gFieldEffectObjectPic_UnusedGrass2[] = INCBIN_U32("graphics/field_effects/pics/unused_grass_2.4bpp");
 const u32 gFieldEffectObjectPic_LongGrass[] = INCBIN_U32("graphics/field_effects/pics/long_grass.4bpp");
diff --git a/src/field_effect_helpers.c b/src/field_effect_helpers.c
index 65617038d1..c3332c7fc6 100755
--- a/src/field_effect_helpers.c
+++ b/src/field_effect_helpers.c
@@ -487,6 +487,8 @@ void UpdateLongGrassFieldEffect(struct Sprite *sprite)
 #undef sCurrentMap
 #undef sObjectMoved
 
+// Effectively unused as it's not possible in vanilla to jump onto long grass (no adjacent ledges, and can't ride the Acro Bike in it).
+// The graphics for this effect do not visually correspond to long grass either. Perhaps these graphics were its original design?
 u32 FldEff_JumpLongGrass(void)
 {
     u8 spriteId;