diff --git a/ide/vs2019/mimalloc.vcxproj b/ide/vs2019/mimalloc.vcxproj
index 56beeff9..5658b536 100644
--- a/ide/vs2019/mimalloc.vcxproj
+++ b/ide/vs2019/mimalloc.vcxproj
@@ -111,7 +111,7 @@
   </ItemDefinitionGroup>
   <ItemDefinitionGroup Condition="'$(Configuration)|$(Platform)'=='Debug|x64'">
     <ClCompile>
-      <WarningLevel>Level4</WarningLevel>
+      <WarningLevel>Level3</WarningLevel>
       <Optimization>Disabled</Optimization>
       <SDLCheck>true</SDLCheck>
       <ConformanceMode>true</ConformanceMode>
diff --git a/include/mimalloc-atomic.h b/include/mimalloc-atomic.h
index 8b254d3e..dff0f011 100644
--- a/include/mimalloc-atomic.h
+++ b/include/mimalloc-atomic.h
@@ -130,7 +130,7 @@ static inline intptr_t mi_atomic_add(volatile _Atomic(intptr_t)* p, intptr_t add
   return (intptr_t)RC64(_InterlockedExchangeAdd)((volatile msc_intptr_t*)p, (msc_intptr_t)add);
 }
 static inline bool mi_atomic_cas_strong(volatile _Atomic(uintptr_t)* p, uintptr_t desired, uintptr_t expected) {
-  return (expected == RC64(_InterlockedCompareExchange)((volatile msc_intptr_t*)p, (msc_intptr_t)desired, (msc_intptr_t)expected));
+  return (expected == (uintptr_t)RC64(_InterlockedCompareExchange)((volatile msc_intptr_t*)p, (msc_intptr_t)desired, (msc_intptr_t)expected));
 }
 static inline bool mi_atomic_cas_weak(volatile _Atomic(uintptr_t)* p, uintptr_t desired, uintptr_t expected) {
   return mi_atomic_cas_strong(p,desired,expected);
diff --git a/src/memory.c b/src/memory.c
index 0ad582cd..f9c53782 100644
--- a/src/memory.c
+++ b/src/memory.c
@@ -71,7 +71,7 @@ bool    _mi_os_is_huge_reserved(void* p);
 typedef uintptr_t mi_region_info_t;
 
 static inline mi_region_info_t mi_region_info_create(void* start, bool is_large, bool is_committed) {
-  return ((uintptr_t)start | ((is_large?1:0) << 1) | (is_committed?1:0));
+  return ((uintptr_t)start | ((uintptr_t)(is_large?1:0) << 1) | (is_committed?1:0));
 }
 
 static inline void* mi_region_info_read(mi_region_info_t info, bool* is_large, bool* is_committed) {
diff --git a/src/options.c b/src/options.c
index 413ea765..4e2bdeaa 100644
--- a/src/options.c
+++ b/src/options.c
@@ -346,7 +346,7 @@ static void mi_option_init(mi_option_desc_t* desc) {
     size_t len = strlen(s);
     if (len >= sizeof(buf)) len = sizeof(buf) - 1;
     for (size_t i = 0; i < len; i++) {
-      buf[i] = toupper(s[i]);
+      buf[i] = (char)toupper(s[i]);
     }
     buf[len] = 0;
     if (buf[0]==0 || strstr("1;TRUE;YES;ON", buf) != NULL) {
diff --git a/src/os.c b/src/os.c
index c6ab4ab6..ed938221 100644
--- a/src/os.c
+++ b/src/os.c
@@ -700,7 +700,7 @@ static bool mi_os_resetx(void* addr, size_t size, bool reset, mi_stats_t* stats)
   void* p = VirtualAlloc(start, csize, MEM_RESET, PAGE_READWRITE);
   mi_assert_internal(p == start);
   #if 1
-  if (p == start) {
+  if (p == start && start != NULL) {
     VirtualUnlock(start,csize); // VirtualUnlock after MEM_RESET removes the memory from the working set
   }
   #endif
diff --git a/src/page-queue.c b/src/page-queue.c
index d613095f..4af70b50 100644
--- a/src/page-queue.c
+++ b/src/page-queue.c
@@ -57,7 +57,7 @@ static inline uint8_t mi_bsr32(uint32_t x);
 static inline uint8_t mi_bsr32(uint32_t x) {
   uint32_t idx;
   _BitScanReverse((DWORD*)&idx, x);
-  return idx;
+  return (uint8_t)idx;
 }
 #elif defined(__GNUC__) || defined(__clang__)
 static inline uint8_t mi_bsr32(uint32_t x) {