diff --git a/src/libultra/io/pfsfreeblocks.c b/src/libultra/io/pfsfreeblocks.c
index af10a5b887..b90979c595 100644
--- a/src/libultra/io/pfsfreeblocks.c
+++ b/src/libultra/io/pfsfreeblocks.c
@@ -1,3 +1,37 @@
 #include "global.h"
+#include "PR/pfs.h"
 
-#pragma GLOBAL_ASM("asm/non_matchings/boot/pfsfreeblocks/osPfsFreeBlocks.s")
+s32 osPfsFreeBlocks(OSPfs* pfs, s32* leftoverBytes) {
+    s32 j;
+    s32 pages = 0;
+    __OSInode inode;
+    s32 ret = 0;
+    u8 bank;
+    s32 offset;
+
+    if (!(pfs->status & PFS_INITIALIZED)) {
+        return PFS_ERR_INVALID;
+    }
+
+    ret = __osCheckId(pfs);
+    if (ret != 0) {
+        return ret;
+    }
+
+    for (bank = PFS_ID_BANK_256K; bank < pfs->banks; bank++) {
+        ret = __osPfsRWInode(pfs, &inode, PFS_READ, bank);
+        if (ret != 0) {
+            return ret;
+        }
+
+        offset = ((bank > PFS_ID_BANK_256K) ? 1 : pfs->inodeStartPage);
+        for (j = offset; j < PFS_INODE_SIZE_PER_PAGE; j++) {
+            if (inode.inodePage[j].ipage == PFS_PAGE_NOT_USED) {
+                pages++;
+            }
+        }
+    }
+
+    *leftoverBytes = pages * PFS_ONE_PAGE * BLOCKSIZE;
+    return 0;
+}