diff --git a/src/common/impl/io_windows.c b/src/common/impl/io_windows.c
index 992a0aded..49b49df09 100644
--- a/src/common/impl/io_windows.c
+++ b/src/common/impl/io_windows.c
@@ -281,7 +281,7 @@ bool ffPathExpandEnv(const char* in, FFstrbuf* out) {
     }
     len /= sizeof(wchar_t); // convert from bytes to characters
 
-    size_t outLen; // in characters, including null terminator
+    SIZE_T outLen; // in characters, including null terminator
     if (!NT_SUCCESS(RtlExpandEnvironmentStrings(NULL, pathInW, len, pathOutW, ARRAY_SIZE(pathOutW), &outLen))) {
         return false;
     }
diff --git a/src/common/windows/nt.h b/src/common/windows/nt.h
index ecbc8da91..38f2f3f37 100644
--- a/src/common/windows/nt.h
+++ b/src/common/windows/nt.h
@@ -616,9 +616,9 @@ static inline uint64_t ffKSystemTimeToUInt64(const volatile KSYSTEM_TIME* pTime)
     uint32_t low, high1, high2;
 
     do {
-        high1 = pTime->High1Time;
-        low = pTime->LowPart;
-        high2 = pTime->High2Time;
+        high1 = (uint32_t) pTime->High1Time;
+        low = (uint32_t) pTime->LowPart;
+        high2 = (uint32_t) pTime->High2Time;
     } while (high1 != high2);
 
     return ((uint64_t) high1 << 32) | low;