diff --git a/ntt_parameters.h b/ntt_parameters.h
index eba9579ab87ca..dc56ab62dd666 100644
--- a/ntt_parameters.h
+++ b/ntt_parameters.h
@@ -34,7 +34,7 @@ template <typename ModularInt>
 void FillWithEveryPower(const ModularInt& base, unsigned int n,
                         std::vector<ModularInt>* row,
                         const typename ModularInt::Params* params) {
-  for (int i = 0; i < n; i++) {
+  for (unsigned int i = 0; i < n; i++) {
     (*row)[i].AddInPlace(base.ModExp(i, params), params);
   }
 }
@@ -183,7 +183,7 @@ rlwe::StatusOr<NttParameters<ModularInt>> InitializeNttParameters(
   // Abort if log_n is non-positive.
   if (log_n <= 0) {
     return absl::InvalidArgumentError("log_n must be positive");
-  } else if (log_n > kMaxLogNumCoeffs) {
+  } else if (static_cast<Uint64>(log_n) > kMaxLogNumCoeffs) {
     return absl::InvalidArgumentError(absl::StrCat(
         "log_n, ", log_n, ", must be less than ", kMaxLogNumCoeffs, "."));
   }
diff --git a/sample_error.h b/sample_error.h
index 7d570c5cd2e7a..b1f19eb952551 100644
--- a/sample_error.h
+++ b/sample_error.h
@@ -57,7 +57,7 @@ static rlwe::StatusOr<std::vector<ModularInt>> SampleFromErrorDistribution(
   Uint64 k;
   typename ModularInt::Int coefficient;
 
-  for (int i = 0; i < num_coeffs; i++) {
+  for (unsigned int i = 0; i < num_coeffs; i++) {
     coefficient = modulus_params->modulus;
     k = variance << 1;
 
diff --git a/symmetric_encryption.h b/symmetric_encryption.h
index 987e86f7a9823..06dabb89502d4 100644
--- a/symmetric_encryption.h
+++ b/symmetric_encryption.h
@@ -630,9 +630,9 @@ class SymmetricRlweKey {
   const typename ModularInt::Params* ModulusParams() const {
     return modulus_params_;
   }
-  const unsigned int BitsPerCoeff() const { return log_t_; }
-  const Uint64 Variance() const { return variance_; }
-  const unsigned int LogT() const { return log_t_; }
+  unsigned int BitsPerCoeff() const { return log_t_; }
+  Uint64 Variance() const { return variance_; }
+  unsigned int LogT() const { return log_t_; }
   const ModularInt& PlaintextModulus() const { return t_mod_; }
   const typename ModularInt::Params* PlaintextModulusParams() const {
     return plaintext_modulus_params_;
@@ -941,7 +941,7 @@ rlwe::StatusOr<std::vector<typename ModularInt::Int>> Decrypt(
   Polynomial<ModularInt> key_powers = key.Key();
   unsigned int ciphertext_len = ciphertext.Len();
 
-  for (int i = 0; i < ciphertext_len; i++) {
+  for (unsigned int i = 0; i < ciphertext_len; i++) {
     // Extract component i.
     RLWE_ASSIGN_OR_RETURN(Polynomial<ModularInt> ci, ciphertext.Component(i));