diff --git a/include/common_structs.h b/include/common_structs.h
index e3d352c136..16222a7037 100644
--- a/include/common_structs.h
+++ b/include/common_structs.h
@@ -191,7 +191,7 @@ typedef struct script_context {
     /* 0x06C */ struct script_context* parentScript; /* brother? */
     /* 0x070 */ s32 functionTemp[4];
     /* 0x080 */ UNK_PTR callFunction;
-    /* 0x084 */ u32 varTable[16];
+    /* 0x084 */ s32 varTable[16];
     /* 0x0C4 */ s32 varFlags[3];
     /* 0x0D0 */ s32 loopStartTable[8];
     /* 0x0F0 */ s32 loopCounterTable[8];
diff --git a/include/functions.h b/include/functions.h
index c533f9d6fd..9f5f91a185 100644
--- a/include/functions.h
+++ b/include/functions.h
@@ -3,6 +3,7 @@
 
 #include "ultra64.h"
 #include "common_structs.h"
+#include "enums.h"
 
 void osCleanupThread(void);
 
@@ -19,6 +20,7 @@ s32 func_800554E8(s32, s32);
 s32 func_800555E4(s32);
 void func_80137D88(s32, f32);
 void func_80137E10(s32, u8, u8, u8);
+f32 update_lerp(EASING easing, f32 start, f32 end, s32 elapsed, s32 duration);
 
 s32 play_sound_at_position(s32 soundID, s32 value2, f32 posX, f32 posY, f32 posZ);
 s32 set_music_track(s32 musicPlayer, s32 songID, s32 variation, s32 unk, s32 volume);
diff --git a/src/code_42e0_len_1f60.c b/src/code_42e0_len_1f60.c
index d7c0efcc80..4144290940 100644
--- a/src/code_42e0_len_1f60.c
+++ b/src/code_42e0_len_1f60.c
@@ -78,7 +78,7 @@ f32 INCLUDE_ASM(code_42e0_len_1f60, sin_deg, f32 x);
 
 f32 INCLUDE_ASM(code_42e0_len_1f60, cos_deg, f32 x);
 
-INCLUDE_ASM(code_42e0_len_1f60, update_lerp);
+f32 INCLUDE_ASM(code_42e0_len_1f60, update_lerp, EASING easing, f32 start, f32 end, s32 elapsed, s32 duration);
 
 INCLUDE_ASM(code_42e0_len_1f60, func_8002A904);
 
diff --git a/src/code_f8f60_len_1560.c b/src/code_f8f60_len_1560.c
index 0935aafadf..ad6c681d63 100644
--- a/src/code_f8f60_len_1560.c
+++ b/src/code_f8f60_len_1560.c
@@ -7,12 +7,29 @@ s32 MakeLerp(script_context* script, s32 initialCall) {
     script->varTable[0xD] = get_variable(script, *ptrReadPos++); // end
     script->varTable[0xF] = get_variable(script, *ptrReadPos++); // duration
     script->varTable[0xB] = get_variable(script, *ptrReadPos++); // easing type
-    script->varTable[0xE] = 0;
+    script->varTable[0xE] = 0; // elapsed
 
     return 2;
 }
 
-INCLUDE_ASM(code_f8f60_len_1560, UpdateLerp);
+s32 UpdateLerp(script_context* script, s32 initialCall) {
+    script->varTable[0x0] = (s32) update_lerp(
+        script->varTable[0xB],
+        (s32) script->varTable[0xC],
+        (s32) script->varTable[0xD],
+        script->varTable[0xE],
+        script->varTable[0xF]
+    );
+
+    if (script->varTable[0xE] >= script->varTable[0xF]) {
+        script->varTable[0x1] = 0; // finished
+    } else {
+        script->varTable[0x1] = 1; // lerping
+    }
+    script->varTable[0xE]++;
+
+    return 2;
+}
 
 INCLUDE_ASM(code_f8f60_len_1560, RandInt);