diff --git a/asm/include/main_02001C80.inc b/asm/include/main_02001CB0.inc
similarity index 100%
rename from asm/include/main_02001C80.inc
rename to asm/include/main_02001CB0.inc
diff --git a/asm/main_02001C80.s b/asm/main_02001CB0.s
similarity index 96%
rename from asm/main_02001C80.s
rename to asm/main_02001CB0.s
index d091a675..9d25f97e 100644
--- a/asm/main_02001C80.s
+++ b/asm/main_02001CB0.s
@@ -1,24 +1,8 @@
 	.include "asm/macros.inc"
-	.include "main_02001C80.inc"
+	.include "main_02001CB0.inc"
 
 	.text
 
-	arm_func_start IntToFixedPoint64
-IntToFixedPoint64: ; 0x02001C80
-	mov r2, #0x10000
-	rsb r2, r2, #0
-	and r3, r1, r2
-	mov r3, r3, lsr #0x10
-	str r3, [r0]
-	mov r3, r1, lsl #0x10
-	str r3, [r0, #4]
-	tst r1, #0x8000
-	ldrne r1, [r0]
-	orrne r1, r1, r2
-	strne r1, [r0]
-	bx lr
-	arm_func_end IntToFixedPoint64
-
 	arm_func_start FixedPoint64ToInt
 FixedPoint64ToInt: ; 0x02001CB0
 	ldmia r0, {r1, r2}
diff --git a/include/main_02001BB4.h b/include/main_02001BB4.h
index 4b282b12..3573a59f 100644
--- a/include/main_02001BB4.h
+++ b/include/main_02001BB4.h
@@ -4,5 +4,6 @@
 #include "util.h"
 
 u32 sub_02001BB4(s32 x, s32 y);
+void IntToFixedPoint64(struct fixed_point_64* out, s32 x);
 
 #endif //PMDSKY_MAIN_02001BB4_H
diff --git a/include/util.h b/include/util.h
index c700f204..0c8843ab 100644
--- a/include/util.h
+++ b/include/util.h
@@ -32,6 +32,13 @@ struct fixed_point {
     s16 fractional;
 };
 
+// 64-bit signed fixed-point number with 16 fraction bits.
+// Represents the number ((upper << 16) + (lower >> 16) + (lower & 0xFFFF) * 2^-16)
+struct fixed_point_64 {
+    s32 upper;  // sign bit, plus the 31 most significant integer bits
+    u32 lower; // the 32 least significant bits (16 integer + 16 fraction)
+};
+
 // Compares two numbers and return the minimum
 #define MIN(A, B) ((A > B) ? B : A)
 
diff --git a/main.lsf b/main.lsf
index ff617db3..a00b20ee 100644
--- a/main.lsf
+++ b/main.lsf
@@ -21,7 +21,7 @@ Static main
 	Object src/main_02001A54.o
 	Object asm/main_02001B0C.o
 	Object src/main_02001BB4.o
-	Object asm/main_02001C80.o
+	Object asm/main_02001CB0.o
 	Object src/main_0200224C.o
 	Object asm/main_020022C4.o
 	Object src/main_0200330C.o
diff --git a/src/main_02001BB4.c b/src/main_02001BB4.c
index 8bbc0f6c..8032a27b 100644
--- a/src/main_02001BB4.c
+++ b/src/main_02001BB4.c
@@ -61,3 +61,12 @@ u32 sub_02001BB4(s32 x, s32 y)
     
     return var_r8;
 }
+
+void IntToFixedPoint64(struct fixed_point_64* out, s32 x)
+{
+    out->upper = (u32) (x & ~0xFFFF) >> 0x10;
+    out->lower = x << 0x10;
+    if (x & 0x8000) {
+        out->upper = out->upper | ~0xFFFF;
+    }
+}