diff --git a/system/lib/libc/emscripten_time.c b/system/lib/libc/emscripten_time.c
index 6f150c1229dfd..88c9c4853db2a 100644
--- a/system/lib/libc/emscripten_time.c
+++ b/system/lib/libc/emscripten_time.c
@@ -19,8 +19,8 @@ __attribute__((__weak__)) int   daylight = 0;
 __attribute__((__weak__)) char *tzname[2] = { 0, 0 };
 
 void _tzset_js(long* timezone, int* daylight, char** tzname);
-time_t _timegm_js(struct tm *tm);
-time_t _mktime_js(struct tm *tm);
+int _timegm_js(struct tm *tm);
+int _mktime_js(struct tm *tm);
 void _localtime_js(const time_t *restrict t, struct tm *restrict tm);
 void _gmtime_js(const time_t *restrict t, struct tm *restrict tm);
 double _emscripten_date_now();
diff --git a/system/lib/libc/musl/arch/emscripten/bits/alltypes.h b/system/lib/libc/musl/arch/emscripten/bits/alltypes.h
index e90252190f63c..f239859acacb6 100644
--- a/system/lib/libc/musl/arch/emscripten/bits/alltypes.h
+++ b/system/lib/libc/musl/arch/emscripten/bits/alltypes.h
@@ -78,12 +78,12 @@ typedef long double double_t;
 #endif
 
 #if defined(__NEED_time_t) && !defined(__DEFINED_time_t)
-typedef int time_t; /* XXX EMSCRIPTEN: ensure it's always 32-bits even in wasm64 */
+typedef _Int64 time_t;
 #define __DEFINED_time_t
 #endif
 
 #if defined(__NEED_suseconds_t) && !defined(__DEFINED_suseconds_t)
-typedef int suseconds_t; /* XXX EMSCRIPTEN: ensure it's always 32-bits even in wasm64 */
+typedef _Int64 suseconds_t;
 #define __DEFINED_suseconds_t
 #endif
 
@@ -248,27 +248,27 @@ typedef unsigned _Int64 ino_t;
 #endif
 
 #if defined(__NEED_dev_t) && !defined(__DEFINED_dev_t)
-typedef unsigned int dev_t;
+typedef unsigned _Int64 dev_t;
 #define __DEFINED_dev_t
 #endif
 
 #if defined(__NEED_blksize_t) && !defined(__DEFINED_blksize_t)
-typedef int blksize_t; /* XXX EMSCRIPTEN: ensure it's always 32-bits even in wasm64 */
-#define __DEFINED_blksize_t
+typedef long blksize_t;
+#define __DEF_Int64
 #endif
 
 #if defined(__NEED_blkcnt_t) && !defined(__DEFINED_blkcnt_t)
-typedef int blkcnt_t;
+typedef _Int64 blkcnt_t;
 #define __DEFINED_blkcnt_t
 #endif
 
 #if defined(__NEED_fsblkcnt_t) && !defined(__DEFINED_fsblkcnt_t)
-typedef unsigned int fsblkcnt_t;
+typedef unsigned _Int64 fsblkcnt_t;
 #define __DEFINED_fsblkcnt_t
 #endif
 
 #if defined(__NEED_fsfilcnt_t) && !defined(__DEFINED_fsfilcnt_t)
-typedef unsigned int fsfilcnt_t;
+typedef unsigned _Int64 fsfilcnt_t;
 #define __DEFINED_fsfilcnt_t
 #endif
 
diff --git a/system/lib/libc/musl/include/inttypes.h b/system/lib/libc/musl/include/inttypes.h
index fd012b0f33964..90c35c8664ae8 100644
--- a/system/lib/libc/musl/include/inttypes.h
+++ b/system/lib/libc/musl/include/inttypes.h
@@ -22,14 +22,14 @@ uintmax_t strtoumax(const char *__restrict, char **__restrict, int);
 intmax_t wcstoimax(const wchar_t *__restrict, wchar_t **__restrict, int);
 uintmax_t wcstoumax(const wchar_t *__restrict, wchar_t **__restrict, int);
 
-#if UINTPTR_MAX == UINT64_MAX
-#define __PRI64  "l"
-#define __PRIPTR "l"
-#elif defined(__EMSCRIPTEN__)
+#if defined(__EMSCRIPTEN__)
 // Under emscripten __PTRDIFF_TYPE__ and therefor intptr_t are defined to
 // be `long int` even on wasm32.
 #define __PRI64  "ll"
 #define __PRIPTR "l"
+#elif UINTPTR_MAX == UINT64_MAX
+#define __PRI64  "l"
+#define __PRIPTR "l"
 #else
 #define __PRI64  "ll"
 #define __PRIPTR ""
diff --git a/tests/core/test_statvfs.c b/tests/core/test_statvfs.c
index 2de11485b03ff..f1cc925d4974a 100644
--- a/tests/core/test_statvfs.c
+++ b/tests/core/test_statvfs.c
@@ -7,6 +7,7 @@
 
 #include <stdio.h>
 #include <errno.h>
+#include <inttypes.h>
 #include <sys/statvfs.h>
 
 int main() {
@@ -17,12 +18,12 @@ int main() {
 
   printf("f_bsize: %lu\n", s.f_bsize);
   printf("f_frsize: %lu\n", s.f_frsize);
-  printf("f_blocks: %u\n", s.f_blocks);
-  printf("f_bfree: %u\n", s.f_bfree);
-  printf("f_bavail: %u\n", s.f_bavail);
+  printf("f_blocks: %" PRId64 "\n", s.f_blocks);
+  printf("f_bfree: %" PRId64 "\n", s.f_bfree);
+  printf("f_bavail: %" PRId64 "\n", s.f_bavail);
   printf("f_files: %d\n", s.f_files > 5);
-  printf("f_ffree: %u\n", s.f_ffree);
-  printf("f_favail: %u\n", s.f_favail);
+  printf("f_ffree: %" PRId64 "\n", s.f_ffree);
+  printf("f_favail: %" PRId64 "\n", s.f_favail);
   printf("f_fsid: %lu\n", s.f_fsid);
   printf("f_flag: %lu\n", s.f_flag);
   printf("f_namemax: %lu\n", s.f_namemax);
diff --git a/tests/utime/test_utime.c b/tests/utime/test_utime.c
index ebc78c5dc6656..76c37e56953e1 100644
--- a/tests/utime/test_utime.c
+++ b/tests/utime/test_utime.c
@@ -7,6 +7,7 @@
 
 #include <assert.h>
 #include <errno.h>
+#include <inttypes.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdlib.h>
@@ -51,9 +52,9 @@ void test() {
   stat("writeable", &s);
   assert(s.st_atime == s.st_mtime);
   time_t diff = s.st_atime - now;
-  if (abs(diff) > 5) {
-    fprintf(stderr, "st_atime: %i, now: %i, diff: %i\n ", s.st_atime, now, diff);
-    assert(abs(diff) <= 5);
+  if (llabs(diff) > 5) {
+    fprintf(stderr, "st_atime: %" PRId64 ", now: %" PRId64 ", diff: %" PRId64 "\n ", s.st_atime, now, diff);
+    assert(llabs(diff) <= 5);
   }
 
   // write permissions aren't checked when setting node