diff --git a/Makefile b/Makefile
index 1c7ae02e3..e1b7210c6 100644
--- a/Makefile
+++ b/Makefile
@@ -318,6 +318,7 @@ ifeq ($(COMPILER), ido)
         src/lib/ultra/io/pfsinitpak2.c
 
     MIPS3_C_FILES := \
+        src/lib/rng.c \
         src/lib/ultra/libc/ll.c \
         src/lib/ultra/libc/llcvt.c
 
@@ -750,6 +751,11 @@ $(B_DIR)/rsp/%.o: $(B_DIR)/rsp/%.bin
 	TOOLCHAIN=$(TOOLCHAIN) ROMID=$(ROMID) tools/mkrawobject $< $@
 
 ifeq ($(COMPILER), ido)
+$(B_DIR)/lib/rng.o: src/lib/rng.c $(ASSETMGR_O_FILES) $(RECOMP_FILES)
+	@mkdir -p $(dir $@)
+	$(CC) -c $(CFLAGS) $(OPT_LVL) -o $@ $<
+	tools/patchmips3 $@ || rm $@
+
 $(B_DIR)/lib/ultra/libc/llcvt.o: src/lib/ultra/libc/llcvt.c $(ASSETMGR_O_FILES) $(RECOMP_FILES)
 	@mkdir -p $(dir $@)
 	$(CC) -c $(CFLAGS) $(OPT_LVL) -o $@ $<
diff --git a/ld/libfiles.jpn-final.inc b/ld/libfiles.jpn-final.inc
index 2a3b003fd..cfdceda97 100644
--- a/ld/libfiles.jpn-final.inc
+++ b/ld/libfiles.jpn-final.inc
@@ -40,7 +40,7 @@
 	build/ROMID/lib/music.o (section); \
 	build/ROMID/lib/memp.o (section); \
 	build/ROMID/lib/mema.o (section); \
-	build/ROMID/lib/rng.o (section); \
+	build/ROMID/lib/rngasm.o (section); \
 	build/ROMID/lib/args.o (section); \
 	build/ROMID/lib/str.o (section); \
 	build/ROMID/lib/ultra/libc/sprintf.o (section); \
diff --git a/ld/libfiles.ntsc-beta.inc b/ld/libfiles.ntsc-beta.inc
index a33cfbd31..9cb456e32 100644
--- a/ld/libfiles.ntsc-beta.inc
+++ b/ld/libfiles.ntsc-beta.inc
@@ -42,7 +42,7 @@
 	build/ROMID/lib/music.o (section); \
 	build/ROMID/lib/memp.o (section); \
 	build/ROMID/lib/mema.o (section); \
-	build/ROMID/lib/rng.o (section); \
+	build/ROMID/lib/rngasm.o (section); \
 	build/ROMID/lib/args.o (section); \
 	build/ROMID/lib/str.o (section); \
 	build/ROMID/lib/ultra/libc/sprintf.o (section); \
diff --git a/ld/libfiles.ntsc-final.inc b/ld/libfiles.ntsc-final.inc
index 0d14cee3a..5d2863913 100644
--- a/ld/libfiles.ntsc-final.inc
+++ b/ld/libfiles.ntsc-final.inc
@@ -40,7 +40,7 @@
 	build/ROMID/lib/music.o (section); \
 	build/ROMID/lib/memp.o (section); \
 	build/ROMID/lib/mema.o (section); \
-	build/ROMID/lib/rng.o (section); \
+	build/ROMID/lib/rngasm.o (section); \
 	build/ROMID/lib/args.o (section); \
 	build/ROMID/lib/str.o (section); \
 	build/ROMID/lib/ultra/libc/sprintf.o (section); \
diff --git a/ld/libfiles.pal-beta.inc b/ld/libfiles.pal-beta.inc
index 2a3b003fd..cfdceda97 100644
--- a/ld/libfiles.pal-beta.inc
+++ b/ld/libfiles.pal-beta.inc
@@ -40,7 +40,7 @@
 	build/ROMID/lib/music.o (section); \
 	build/ROMID/lib/memp.o (section); \
 	build/ROMID/lib/mema.o (section); \
-	build/ROMID/lib/rng.o (section); \
+	build/ROMID/lib/rngasm.o (section); \
 	build/ROMID/lib/args.o (section); \
 	build/ROMID/lib/str.o (section); \
 	build/ROMID/lib/ultra/libc/sprintf.o (section); \
diff --git a/ld/libfiles.pal-final.inc b/ld/libfiles.pal-final.inc
index 2a3b003fd..cfdceda97 100644
--- a/ld/libfiles.pal-final.inc
+++ b/ld/libfiles.pal-final.inc
@@ -40,7 +40,7 @@
 	build/ROMID/lib/music.o (section); \
 	build/ROMID/lib/memp.o (section); \
 	build/ROMID/lib/mema.o (section); \
-	build/ROMID/lib/rng.o (section); \
+	build/ROMID/lib/rngasm.o (section); \
 	build/ROMID/lib/args.o (section); \
 	build/ROMID/lib/str.o (section); \
 	build/ROMID/lib/ultra/libc/sprintf.o (section); \
diff --git a/src/include/lib/rng.h b/src/include/lib/rng.h
index d5231d39d..32741640f 100644
--- a/src/include/lib/rng.h
+++ b/src/include/lib/rng.h
@@ -5,7 +5,6 @@
 #include "types.h"
 
 u32 random(void);
-void rngSetSeed(u32 seed);
 u32 rngRotateSeed(u64 *value);
 
 #endif
diff --git a/src/lib/main.c b/src/lib/main.c
index ba388a23d..43fca9c04 100644
--- a/src/lib/main.c
+++ b/src/lib/main.c
@@ -70,6 +70,10 @@
 #include "data.h"
 #include "types.h"
 
+// mainLoop calls rngSetSeed with a u32 argument,
+// but the function takes a u64 so an incorrect declaration is needed.
+void rngSetSeed(u32 seed);
+
 bool var8005d9b0 = false;
 s32 g_StageNum = STAGE_TITLE;
 u32 g_MainMemaHeapSize = 1024 * 300;
diff --git a/src/lib/rng.c b/src/lib/rng.c
new file mode 100644
index 000000000..6bee7e7f3
--- /dev/null
+++ b/src/lib/rng.c
@@ -0,0 +1,41 @@
+#include <ultra64.h>
+#include "constants.h"
+#include "bss.h"
+#include "lib/rng.h"
+#include "data.h"
+#include "types.h"
+
+u64 g_RngSeed = 0xab8d9f7781280783;
+
+/**
+ * Generate a random number between 0 and 4294967295.
+ */
+u32 random(void)
+{
+	g_RngSeed = ((g_RngSeed << 63) >> 31 | (g_RngSeed << 31) >> 32) ^ (g_RngSeed << 44) >> 32;
+	g_RngSeed = ((g_RngSeed >> 20) & 0xfff) ^ g_RngSeed;
+
+	return g_RngSeed;
+}
+
+/**
+ * Set the given seed as the RNG seed. Add 1 to make sure it isn't 0.
+ */
+void rngSetSeed(u64 seed)
+{
+	g_RngSeed = seed + 1;
+}
+
+/**
+ * Rotate the given seed using the same algorithm as random().
+ *
+ * Store the new 64-bit seed at the pointed address and return the same seed
+ * cast as a u32.
+ */
+u32 rngRotateSeed(u64 *seed)
+{
+	*seed = ((*seed << 63) >> 31 | (*seed << 31) >> 32) ^ (*seed << 44) >> 32;
+	*seed = ((*seed >> 20) & 0xfff) ^ *seed;
+
+	return *seed;
+}
diff --git a/src/lib/rng.s b/src/lib/rngasm.s
similarity index 98%
rename from src/lib/rng.s
rename to src/lib/rngasm.s
index c94a82a22..30f97bed0 100644
--- a/src/lib/rng.s
+++ b/src/lib/rngasm.s
@@ -36,7 +36,7 @@ glabel random
 	dsra32  $v0, $v0, 0
 
 /**
- * void rngSetSeed(u32 seed)
+ * void rngSetSeed(u64 seed)
  *
  * Set the given seed as the RNG seed. Add 1 to make sure it isn't 0.
  */