diff --git a/include/bmarch.h b/include/bmarch.h
index c93e3b22..08d2e46a 100644
--- a/include/bmarch.h
+++ b/include/bmarch.h
@@ -11,7 +11,7 @@ s32 IsBallista(struct Trap* trap);
 int sub_8037AC0(struct Trap* trap);
 int sub_8037AEC(struct Trap* trap);
 int GetBallistaItemUses(struct Trap* trap);
-// ??? ClearBallistaOccupied(???);
-// ??? SetBallistaOccupied(???);
+void ClearBallistaOccupied(struct Trap* trap);
+void SetBallistaOccupied(struct Trap* trap);
 
 #endif // GUARD_BMARCH_H
diff --git a/include/bmunit.h b/include/bmunit.h
index 0c39c029..545bf0cc 100644
--- a/include/bmunit.h
+++ b/include/bmunit.h
@@ -463,6 +463,7 @@ struct Unit* GetUnit(int id);
 const struct ClassData* GetClassData(int classId);
 const struct CharacterData* GetCharacterData(int charId);
 void UnitRemoveItem(struct Unit* unit, int slot);
+s32 CanUnitCrossTerrain(struct Unit* unit, int terrain);
 
 #define UNIT_IS_VALID(aUnit) ((aUnit) && (aUnit)->pCharacterData)
 #define UNIT_CHAR_ID(aUnit) ((aUnit)->pCharacterData->number)
diff --git a/src/bmtarget.c b/src/bmtarget.c
index 9b07d9d6..b0d76501 100644
--- a/src/bmtarget.c
+++ b/src/bmtarget.c
@@ -18,8 +18,6 @@
 
 struct Unit* EWRAM_DATA gSubjectUnit = NULL;
 
-s8 CanUnitCrossTerrain(struct Unit* unit, int terrain);
-
 void ForEachUnitInMovement(void(*func)(struct Unit* unit)) {
     int ix;
     int iy;
@@ -306,7 +304,7 @@ void TryAddToDropTargetList(int x, int y) {
         return;
     }
 
-    if (!CanUnitCrossTerrain(GetUnit(gSubjectUnit->rescue), gBmMapTerrain[y][x])) {
+    if (!(s8)CanUnitCrossTerrain(GetUnit(gSubjectUnit->rescue), gBmMapTerrain[y][x])) {
         return;
     }
 
@@ -809,7 +807,7 @@ void AddAsTarget_IfPositionCleanForSummon(int x, int y) {
         return;
     }
 
-    if (!CanUnitCrossTerrain(gSubjectUnit, gBmMapTerrain[y][x])) {
+    if (!(s8)CanUnitCrossTerrain(gSubjectUnit, gBmMapTerrain[y][x])) {
         return;
     }
 
@@ -841,7 +839,7 @@ void sub_8025CD8(int x, int y) {
         return;
     }
 
-    if (!CanUnitCrossTerrain(gSubjectUnit, gBmMapTerrain[y][x])) {
+    if (!(s8)CanUnitCrossTerrain(gSubjectUnit, gBmMapTerrain[y][x])) {
         return;
     }
 
@@ -1272,7 +1270,7 @@ void TryAddToMineTargetList(int x, int y) {
         return;
     }
 
-    if (!CanUnitCrossTerrain(gSubjectUnit, gBmMapTerrain[y][x])) {
+    if (!(s8)CanUnitCrossTerrain(gSubjectUnit, gBmMapTerrain[y][x])) {
         return;
     }
 
diff --git a/src/bmunit.c b/src/bmunit.c
index a30de742..27b43199 100644
--- a/src/bmunit.c
+++ b/src/bmunit.c
@@ -989,7 +989,7 @@ void UnitChangeFaction(struct Unit* unit, int faction) {
         GetUnit(newUnit->rescue)->rescue = newUnit->index;
 }
 
-inline s8 CanUnitCrossTerrain(struct Unit* unit, int terrain) {
+inline s32 CanUnitCrossTerrain(struct Unit* unit, int terrain) {
     const s8* lookup = GetUnitMovementCost(unit);
     return (lookup[terrain] > 0) ? TRUE : FALSE;
 }
@@ -1036,7 +1036,7 @@ void UnitGetDeathDropLocation(struct Unit* unit, int* xOut, int* yOut) {
             if (gBmMapHidden[iy][ix] & HIDDEN_BIT_UNIT)
                 continue;
 
-            if (!CanUnitCrossTerrain(rescuee, gBmMapTerrain[iy][ix]))
+            if (!(s8)CanUnitCrossTerrain(rescuee, gBmMapTerrain[iy][ix]))
                 continue;
 
             distance = RECT_DISTANCE(ix, iy, unit->xPos, unit->yPos);
diff --git a/src/bmusemind.c b/src/bmusemind.c
index 165aff1b..ab9312ef 100644
--- a/src/bmusemind.c
+++ b/src/bmusemind.c
@@ -25,8 +25,6 @@
 #include "bmmind.h"
 #include "bmusemind.h"
 
-s8 CanUnitCrossTerrain(struct Unit* unit, int terrain);
-
  struct ProcCmd CONST_DATA ProcScr_PostWarpStaffAction[] = {
     PROC_SLEEP(0),
     PROC_CALL_2(PostWarpStaff_ExecTrap),
@@ -142,7 +140,7 @@ void GetRescueStaffeePosition(struct Unit* unit, struct Unit* target, int* xOut,
                 continue;
             }
 
-            if (!CanUnitCrossTerrain(target, gBmMapTerrain[iy][ix])) {
+            if (!(s8)CanUnitCrossTerrain(target, gBmMapTerrain[iy][ix])) {
                 continue;
             }
 
@@ -181,7 +179,7 @@ void GetRescueStaffeePosition(struct Unit* unit, struct Unit* target, int* xOut,
                 continue;
             }
 
-            if (!CanUnitCrossTerrain(target, gBmMapTerrain[iy][ix])) {
+            if (!(s8)CanUnitCrossTerrain(target, gBmMapTerrain[iy][ix])) {
                 continue;
             }
 
diff --git a/src/fogmap.c b/src/fogmap.c
index c1d04a1f..73e85e20 100644
--- a/src/fogmap.c
+++ b/src/fogmap.c
@@ -8,8 +8,6 @@
 #include "hardware.h"
 #include "bmudisp.h"
 
-s8 CanUnitCrossTerrain(struct Unit* unit, int terrain);
-
 void UpdateMapViewWithFog(int vision_range)
 {
     if (vision_range < 0)
@@ -51,7 +49,7 @@ void FillWarpRangeMap(struct Unit *unit_act, struct Unit *unit_tar) {
                 if (gBmMapMovement[y][x] > 0x78)
                     continue;
                 
-                if (CanUnitCrossTerrain(unit_tar, gBmMapTerrain[y][x]) &&
+                if ((s8)CanUnitCrossTerrain(unit_tar, gBmMapTerrain[y][x]) &&
                     0 == gBmMapUnit[y][x])
                     continue;
                     
@@ -64,7 +62,7 @@ void FillWarpRangeMap(struct Unit *unit_act, struct Unit *unit_tar) {
                 if (gBmMapMovement[y][x] > 0x78)
                     continue;
                 
-                if (CanUnitCrossTerrain(unit_tar, gBmMapTerrain[y][x]) &&
+                if ((s8)CanUnitCrossTerrain(unit_tar, gBmMapTerrain[y][x]) &&
                     0 == gBmMapUnit[y][x] &&
                     0 != gBmMapFog[y][x])
                     continue;
diff --git a/src/mapanim_summon.c b/src/mapanim_summon.c
index d6eda926..3b63b93f 100644
--- a/src/mapanim_summon.c
+++ b/src/mapanim_summon.c
@@ -202,9 +202,6 @@ void ProcSummonDK_ResetCounter(struct SumProc* proc)
 
 s8 SelectSummonPos(int x, int y, struct SumThing* result)
 {
-    // It is very strange that in this function, CanUnitCrossTerrain should return as int(*)(Unit*, int)
-    extern int CanUnitCrossTerrain(struct Unit* unit, int terrain);
-
     struct SumThing array[9];
     u8 chosen, count = 0;
     short iy, ix;