diff --git a/libc/stdio/stdio.cpp b/libc/stdio/stdio.cpp
index 46d717a..b4b2a36 100644
--- a/libc/stdio/stdio.cpp
+++ b/libc/stdio/stdio.cpp
@@ -581,7 +581,7 @@
 
 int fseeko64(FILE* fp, off64_t offset, int whence) {
   CHECK_FP(fp);
-  return __fseeko64(fp, offset, whence, 8*sizeof(off_t));
+  return __fseeko64(fp, offset, whence, 8*sizeof(off64_t));
 }
 
 int fsetpos(FILE* fp, const fpos_t* pos) {