diff --git a/avx.cc b/avx.cc
index d33f8e5..89a6e88 100644
--- a/avx.cc
+++ b/avx.cc
@@ -102,7 +102,7 @@ std::string Avx::Avx256(int rounds) {
     x[2] = _mm256_mul_pd(minus_four, a[2]);
     x[3] = _mm256_mul_pd(minus_four, a[3]);
   }
-  for (int k = 1; k < 4; k++) {
+  for (int k = 0; k < 4; k++) {
     for (int i = 0; i < 4; i++) {
       if (gross_x[k][i] != gross_x[k][0]) {
         return "avx256 pd";
@@ -140,7 +140,7 @@ std::string Avx::Avx256FMA(int rounds) {
     x[2] = _mm256_mul_pd(minus_four, a[2]);
     x[3] = _mm256_mul_pd(minus_four, a[3]);
   }
-  for (int k = 1; k < 4; k++) {
+  for (int k = 0; k < 4; k++) {
     for (int i = 0; i < 4; i++) {
       if (gross_x[k][i] != gross_x[k][0]) {
         return "avx256 pd";
@@ -182,7 +182,7 @@ std::string Avx::Avx512(int rounds) {
     x[3] = _mm512_mul_pd(minus_four, a[3]);
   }
 
-  for (int k = 1; k < 4; k++) {
+  for (int k = 0; k < 4; k++) {
     for (int i = 0; i < 7; i++) {
       if (gross_x[k][i] != gross_x[k][0]) {
         return "avx512 pd";
diff --git a/cpu_check.cc b/cpu_check.cc
index f250823..a2c2d5b 100644
--- a/cpu_check.cc
+++ b/cpu_check.cc
@@ -444,8 +444,9 @@ Worker::Choices Worker::MakeChoices(BufferSet *b) {
       Json("hash", c.hasher->Name()), ", ",
       Json("copy", MalignBuffer::ToString(c.copy_method)), ", ",
       Json("memset", c.use_repstos ? "rep;sto" : "memset"), ", ",
-      JsonBool("madvise", c.madvise), ", ", Json("size", c.buf_size), ", ",
-      Json("pid", pid_), ", ", Json("round", round_), ", ", c.hole.ToString());
+      JsonBool("madvise", c.madvise), ", ",
+      Json("size", static_cast<uint64_t>(c.buf_size)), ", ", Json("pid", pid_),
+      ", ", Json("round", round_), ", ", c.hole.ToString());
 
   return c;
 }
diff --git a/malign_buffer.cc b/malign_buffer.cc
index 5845ffb..3c1a227 100644
--- a/malign_buffer.cc
+++ b/malign_buffer.cc
@@ -235,8 +235,8 @@ std::string MalignBuffer::Syndrome(const MalignBuffer &that) const {
 std::string MalignBuffer::CorruptionSyndrome(const MalignBuffer &that) const {
   std::stringstream s;
   if (size() != that.size()) {
-    s << Json("unequalSizeThis", size()) << ", "
-      << Json("unequalSizeThat", that.size());
+    s << Json("unequalSizeThis", static_cast<uint64_t>(size())) << ", "
+      << Json("unequalSizeThat", static_cast<uint64_t>(that.size()));
     return s.str();
   }
   bool failed_memcmp = memcmp(data(), that.data(), that.size());
diff --git a/malign_buffer.h b/malign_buffer.h
index ceee77b..f8dda3c 100644
--- a/malign_buffer.h
+++ b/malign_buffer.h
@@ -28,8 +28,8 @@ class MalignBuffer {
  public:
   struct PunchedHole {
     std::string ToString() const;
-    size_t start = 0;
-    size_t length = 0;
+    uint64_t start = 0;
+    uint64_t length = 0;
     unsigned char v = 0x53;
   };
 
diff --git a/silkscreen.cc b/silkscreen.cc
index d18fcc2..c475235 100644
--- a/silkscreen.cc
+++ b/silkscreen.cc
@@ -72,8 +72,8 @@ absl::Status Silkscreen::CheckMySlots(int tid, uint64_t round) const {
     const char v = *data(k);
     if (v == expected) continue;
     error_count++;
-    last_error = absl::StrCat(Json("position", k), ", ", Json("is", v), ", ",
-                              Json("expected", expected));
+    last_error = absl::StrCat(Json("position", static_cast<uint64_t>(k)), ", ",
+                              Json("is", v), ", ", Json("expected", expected));
   }
   if (slot_count(tid) != slots_read) {
     last_error = absl::StrCat(Json("read", slots_read), ", ",