diff --git a/include/mimalloc/prim.h b/include/mimalloc/prim.h
index 606b7199..bddd66e9 100644
--- a/include/mimalloc/prim.h
+++ b/include/mimalloc/prim.h
@@ -22,14 +22,14 @@ terms of the MIT license. A copy of the license can be found in the file
 
 // OS memory configuration
 typedef struct mi_os_mem_config_s {
-  size_t  page_size;            // default to 4KiB
-  size_t  large_page_size;      // 0 if not supported, usually 2MiB (4MiB on Windows)
-  size_t  alloc_granularity;    // smallest allocation size (usually 4KiB, on Windows 64KiB)
-  size_t  physical_memory;      // physical memory size
-  size_t  virtual_address_bits; // usually 48 or 56 bits on 64-bit systems. (used to determine secure randomization)
-  bool    has_overcommit;       // can we reserve more memory than can be actually committed?
-  bool    has_partial_free;     // can allocated blocks be freed partially? (true for mmap, false for VirtualAlloc)
-  bool    has_virtual_reserve;  // supports virtual address space reservation? (if true we can reserve virtual address space without using commit or physical memory)
+  size_t  page_size;              // default to 4KiB
+  size_t  large_page_size;        // 0 if not supported, usually 2MiB (4MiB on Windows)
+  size_t  alloc_granularity;      // smallest allocation size (usually 4KiB, on Windows 64KiB)
+  size_t  physical_memory_in_kib; // physical memory size in KiB
+  size_t  virtual_address_bits;   // usually 48 or 56 bits on 64-bit systems. (used to determine secure randomization)
+  bool    has_overcommit;         // can we reserve more memory than can be actually committed?
+  bool    has_partial_free;       // can allocated blocks be freed partially? (true for mmap, false for VirtualAlloc)
+  bool    has_virtual_reserve;    // supports virtual address space reservation? (if true we can reserve virtual address space without using commit or physical memory)
 } mi_os_mem_config_t;
 
 // Initialize
@@ -124,7 +124,7 @@ void _mi_prim_thread_associate_default_heap(mi_heap_t* heap);
 //-------------------------------------------------------------------
 // Access to TLS (thread local storage) slots.
 // We need fast access to both a unique thread id (in `free.c:mi_free`) and
-// to a thread-local heap pointer (in `alloc.c:mi_malloc`). 
+// to a thread-local heap pointer (in `alloc.c:mi_malloc`).
 // To achieve this we use specialized code for various platforms.
 //-------------------------------------------------------------------
 
diff --git a/src/os.c b/src/os.c
index 61c9eebf..2472b803 100644
--- a/src/os.c
+++ b/src/os.c
@@ -18,17 +18,17 @@ terms of the MIT license. A copy of the license can be found in the file
 ----------------------------------------------------------- */
 #ifndef MI_DEFAULT_VIRTUAL_ADDRESS_BITS
 #if MI_INTPTR_SIZE < 8
-#define MI_DEFAULT_VIRTUAL_ADDRESS_BITS   32
+#define MI_DEFAULT_VIRTUAL_ADDRESS_BITS     32
 #else
-#define MI_DEFAULT_VIRTUAL_ADDRESS_BITS   48
+#define MI_DEFAULT_VIRTUAL_ADDRESS_BITS     48
 #endif
 #endif
 
-#ifndef MI_DEFAULT_PHYSICAL_MEMORY
+#ifndef MI_DEFAULT_PHYSICAL_MEMORY_IN_KIB
 #if MI_INTPTR_SIZE < 8
-#define MI_DEFAULT_PHYSICAL_MEMORY    4*MI_GiB
+#define MI_DEFAULT_PHYSICAL_MEMORY_IN_KIB   4*MI_MiB    // 4 GiB
 #else
-#define MI_DEFAULT_PHYSICAL_MEMORY    32*MI_GiB
+#define MI_DEFAULT_PHYSICAL_MEMORY_IN_KIB   32*MI_MiB   // 32 GiB
 #endif
 #endif
 
@@ -36,7 +36,7 @@ static mi_os_mem_config_t mi_os_mem_config = {
   4096,     // page size
   0,        // large page size (usually 2MiB)
   4096,     // allocation granularity
-  MI_DEFAULT_PHYSICAL_MEMORY,
+  MI_DEFAULT_PHYSICAL_MEMORY_IN_KIB,
   MI_DEFAULT_VIRTUAL_ADDRESS_BITS,
   true,     // has overcommit?  (if true we use MAP_NORESERVE on mmap systems)
   false,    // can we partially free allocated blocks? (on mmap systems we can free anywhere in a mapped range, but on Windows we must free the entire span)
diff --git a/src/prim/unix/prim.c b/src/prim/unix/prim.c
index 46869c86..6103b4e2 100644
--- a/src/prim/unix/prim.c
+++ b/src/prim/unix/prim.c
@@ -142,8 +142,9 @@ void _mi_prim_mem_init( mi_os_mem_config_t* config )
     config->alloc_granularity = (size_t)psize;
     #if defined(_SC_PHYS_PAGES)
     long pphys = sysconf(_SC_PHYS_PAGES);
-    if (pphys > 0 && (size_t)pphys < (SIZE_MAX/(size_t)psize)) {
-      config->physical_memory = (size_t)pphys * (size_t)psize;
+    const size_t psize_in_kib = (size_t)psize / MI_KiB;
+    if (psize_in_kib > 0 && pphys > 0 && (size_t)pphys <= (SIZE_MAX/psize_in_kib)) {
+      config->physical_memory_in_kib = (size_t)pphys * psize_in_kib;
     }
     #endif
   }
diff --git a/src/prim/windows/prim.c b/src/prim/windows/prim.c
index aa79eb91..20f833bd 100644
--- a/src/prim/windows/prim.c
+++ b/src/prim/windows/prim.c
@@ -154,8 +154,8 @@ void _mi_prim_mem_init( mi_os_mem_config_t* config )
     if (pGetPhysicallyInstalledSystemMemory != NULL) {
       ULONGLONG memInKiB = 0;
       if ((*pGetPhysicallyInstalledSystemMemory)(&memInKiB)) {
-        if (memInKiB > 0 && memInKiB < (SIZE_MAX / MI_KiB)) {
-          config->physical_memory = (size_t)memInKiB * MI_KiB;
+        if (memInKiB > 0 && memInKiB <= SIZE_MAX) {
+          config->physical_memory_in_kib = (size_t)memInKiB;
         }
       }
     }
@@ -643,7 +643,7 @@ static void NTAPI mi_win_main(PVOID module, DWORD reason, LPVOID reserved) {
   }
   else if (reason==DLL_THREAD_DETACH && !_mi_is_redirected()) {
     _mi_thread_done(NULL);
-  }    
+  }
 }