diff --git a/source/lib/sysdep/acpi.cpp b/source/lib/sysdep/acpi.cpp
index 5eaa45674a..fd3b6cb8c8 100644
--- a/source/lib/sysdep/acpi.cpp
+++ b/source/lib/sysdep/acpi.cpp
@@ -63,7 +63,7 @@ static u8 ComputeChecksum(PCV_u8 buf, size_t numBytes)
 	// (can't use std::accumulate - we need 8-bit wraparound)
 	u8 sum = 0;
 	for(PCV_u8 p = buf; p < buf+numBytes; p++)
-		sum = u8(sum + *p);
+		sum = u8((sum + *p) & 0xFF);
 	return sum;
 }
 
diff --git a/source/lib/sysdep/arch/x86_x64/x86_x64.cpp b/source/lib/sysdep/arch/x86_x64/x86_x64.cpp
index d066a6dab2..672d4c0c63 100644
--- a/source/lib/sysdep/arch/x86_x64/x86_x64.cpp
+++ b/source/lib/sysdep/arch/x86_x64/x86_x64.cpp
@@ -45,7 +45,7 @@
 #endif
 
 #define CPUID_INTRINSIC 0
-#if MSC_VERSION > 1500 || (MSC_VERSION == 1500 && _MSC_FULL_VER >= 150030729)	// __cpuidex available on VC10+ and VC9 SP1 (allows setting ecx beforehand)
+#if defined(_MSC_FULL_VER) && _MSC_FULL_VER >= 150030729	// __cpuidex available on VC10+ and VC9 SP1 (allows setting ecx beforehand)
 # undef CPUID_INTRINSIC
 # define CPUID_INTRINSIC 1
 #else