diff --git a/src/lib/mac/kmac/kmac.cpp b/src/lib/mac/kmac/kmac.cpp
index 63f99b875a7..62ab1a4f3a3 100644
--- a/src/lib/mac/kmac/kmac.cpp
+++ b/src/lib/mac/kmac/kmac.cpp
@@ -46,7 +46,7 @@ size_t left_or_right_encode(size_t s, T& output_container) {
       i = 1;
    }
    if(IS_LEFT_ENCODE) {
-      output_container.push_back(i);
+      output_container.push_back(static_cast<uint8_t>(i));
       bytes_appended++;
    }
    // big endian encoding of s
@@ -55,7 +55,7 @@ size_t left_or_right_encode(size_t s, T& output_container) {
       bytes_appended++;
    }
    if(!IS_LEFT_ENCODE) {
-      output_container.push_back(i);
+      output_container.push_back(static_cast<uint8_t>(i));
       bytes_appended++;
    }
    return bytes_appended;
@@ -154,7 +154,7 @@ void KMAC256::start_msg(const uint8_t nonce[], size_t nonce_len) {
    m_hash.absorb(std::span(newX_head));
 }
 
-KMAC256::KMAC256(uint32_t output_bit_length) :
+KMAC256::KMAC256(size_t output_bit_length) :
       m_output_bit_length(output_bit_length), m_hash(output_bit_length, 512, 00, 2), m_pad_byte_length(136) {
    // ensure valid output length
    byte_len_from_bit_len(m_output_bit_length);
diff --git a/src/lib/mac/kmac/kmac.h b/src/lib/mac/kmac/kmac.h
index 97722bbe2d2..e2cee93f82d 100644
--- a/src/lib/mac/kmac/kmac.h
+++ b/src/lib/mac/kmac/kmac.h
@@ -28,7 +28,7 @@ class KMAC256 final : public MessageAuthenticationCode {
       Key_Length_Specification key_spec() const override;
 
       void start_msg(const uint8_t nonce[], size_t nonce_len) override;
-      explicit KMAC256(uint32_t output_byte_length);
+      explicit KMAC256(size_t output_byte_length);
 
       KMAC256(const KMAC256&) = delete;
       KMAC256& operator=(const KMAC256&) = delete;