diff --git a/src/system/boot/platform/efi/video.cpp b/src/system/boot/platform/efi/video.cpp
index aa96c96d56..3399c3b117 100644
--- a/src/system/boot/platform/efi/video.cpp
+++ b/src/system/boot/platform/efi/video.cpp
@@ -84,7 +84,7 @@ static video_mode*
 closest_video_mode(uint32 width, uint32 height, uint32 depth)
 {
 	video_mode *bestMode = NULL;
-	uint32 bestDiff = 0;
+	int64 bestDiff = 0;
 
 	video_mode *mode = NULL;
 	while ((mode = (video_mode*)list_get_next_item(&sModeList, mode)) != NULL) {
@@ -94,8 +94,9 @@ closest_video_mode(uint32 width, uint32 height, uint32 depth)
 			continue;
 		}
 
-		uint32 diff = 2 * abs(mode->width - width) + abs(mode->height - height)
-			+ abs(mode->bits_per_pixel - depth);
+		int64 diff = 2 * abs((int64)mode->width - width)
+			+ abs((int64)mode->height - height)
+			+ abs((int64)mode->bits_per_pixel - depth);
 
 		if (bestMode == NULL || bestDiff > diff) {
 			bestMode = mode;
diff --git a/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp b/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp
index 8639327b20..8d33b7ceb5 100644
--- a/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp
+++ b/src/system/libroot/posix/string/arch/x86_64/arch_string.cpp
@@ -15,6 +15,15 @@
 namespace {
 
 
+// __m128i resolves to a type with an attribute, which can't get into the
+// template signature, resulting in a warning. Nonetheless the code is what we
+// expect, so we silent the warning.
+#pragma GCC diagnostic push
+#if defined __GNUC__ && __GNUC__ >= 6
+#pragma GCC diagnostic ignored "-Wignored-attributes"
+#endif
+
+
 template<template<size_t N> class Generator, unsigned N, unsigned ...Index>
 struct GenerateTable : GenerateTable<Generator, N - 1,  N - 1, Index...> {
 };
@@ -32,6 +41,9 @@ struct GenerateTable<Generator, 0, Index...>
 };
 
 
+#pragma GCC diagnostic pop
+
+
 static inline void memcpy_repmovs(uint8_t* destination, const uint8_t* source,
 	size_t length)
 {