diff --git a/src/prim/unix/prim.c b/src/prim/unix/prim.c
index d99f6097..91fa6508 100644
--- a/src/prim/unix/prim.c
+++ b/src/prim/unix/prim.c
@@ -37,6 +37,7 @@ terms of the MIT license. A copy of the license can be found in the file
   #include <sys/mman.h>
   #endif
 #elif defined(__APPLE__)
+  #include <AvailabilityMacros.h>
   #include <TargetConditionals.h>
   #if !TARGET_IOS_IPHONE && !TARGET_IOS_SIMULATOR
   #include <mach/vm_statistics.h>
@@ -55,12 +56,14 @@ terms of the MIT license. A copy of the license can be found in the file
   #include <sys/syscall.h>
 #endif
 
+
 //------------------------------------------------------------------------------------
 // Use syscalls for some primitives to allow for libraries that override open/read/close etc.
 // and do allocation themselves; using syscalls prevents recursion when mimalloc is 
 // still initializing (issue #713)
 //------------------------------------------------------------------------------------
 
+
 #if defined(MI_HAS_SYSCALL_H) && defined(SYS_open) && defined(SYS_close) && defined(SYS_read) && defined(SYS_access)
 
 static int mi_prim_open(const char* fpath, int open_flags) {
@@ -76,7 +79,9 @@ static int mi_prim_access(const char *fpath, int mode) {
   return syscall(SYS_access,fpath,mode);
 }
 
-#elif !defined(__APPLE__)  // avoid unused warnings
+#elif (!defined(__APPLE__) || MAC_OS_X_VERSION_MIN_REQUIRED < 1070)  // avoid unused warnings on macOS
+
+#include <fcntl.h>
 
 static int mi_prim_open(const char* fpath, int open_flags) {
   return open(fpath,open_flags);
@@ -731,28 +736,20 @@ bool _mi_prim_getenv(const char* name, char* result, size_t result_size) {
 // Random
 //----------------------------------------------------------------
 
-#if defined(__APPLE__)
-
-#include <AvailabilityMacros.h>
-#if defined(MAC_OS_X_VERSION_10_10) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_10
+#if defined(MAC_OS_X_VERSION_10_15) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_15 && MAC_OS_X_VERSION_MIN_REQUIRED >= 1070
 #include <CommonCrypto/CommonCryptoError.h>
 #include <CommonCrypto/CommonRandom.h>
-#endif
+
 bool _mi_prim_random_buf(void* buf, size_t buf_len) {
-  #if defined(MAC_OS_X_VERSION_10_15) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_15
-    // We prefere CCRandomGenerateBytes as it returns an error code while arc4random_buf
-    // may fail silently on macOS. See PR #390, and <https://opensource.apple.com/source/Libc/Libc-1439.40.11/gen/FreeBSD/arc4random.c.auto.html>
-    return (CCRandomGenerateBytes(buf, buf_len) == kCCSuccess);
-  #else
-    // fall back on older macOS
-    arc4random_buf(buf, buf_len);
-    return true;
-  #endif
+  // We prefere CCRandomGenerateBytes as it returns an error code while arc4random_buf
+  // may fail silently on macOS. See PR #390, and <https://opensource.apple.com/source/Libc/Libc-1439.40.11/gen/FreeBSD/arc4random.c.auto.html>
+  return (CCRandomGenerateBytes(buf, buf_len) == kCCSuccess);  
 }
 
 #elif defined(__ANDROID__) || defined(__DragonFly__) || \
       defined(__FreeBSD__) || defined(__NetBSD__) || defined(__OpenBSD__) || \
-      defined(__sun) 
+      defined(__sun) || \
+      (defined(MAC_OS_X_VERSION_10_10) && MAC_OS_X_VERSION_MAX_ALLOWED >= MAC_OS_X_VERSION_10_10 && MAC_OS_X_VERSION_MIN_REQUIRED >= 1070)
 
 #include <stdlib.h>
 bool _mi_prim_random_buf(void* buf, size_t buf_len) {
@@ -760,7 +757,7 @@ bool _mi_prim_random_buf(void* buf, size_t buf_len) {
   return true;
 }
 
-#elif defined(__linux__) || defined(__HAIKU__)
+#elif defined(__APPLE__) || defined(__linux__) || defined(__HAIKU__)   // for old apple versions < 1070 (issue #829)
 
 #include <sys/types.h>
 #include <sys/stat.h>