diff --git a/src/futils.cpp b/src/futils.cpp
index 380c5386..af969ed4 100644
--- a/src/futils.cpp
+++ b/src/futils.cpp
@@ -71,7 +71,7 @@ std::string getEnv(int env_var) {
 
 /// @brief Convert an integer value to its hex character.
 char to_hex(char code) {
-  static char hex[] = "0123456789abcdef";
+  static const char hex[] = "0123456789abcdef";
   return hex[code & 15];
 }
 
diff --git a/src/pngchunk_int.cpp b/src/pngchunk_int.cpp
index 29875907..342cc7bf 100644
--- a/src/pngchunk_int.cpp
+++ b/src/pngchunk_int.cpp
@@ -476,10 +476,11 @@ DataBuf PngChunk::readRawProfile(const DataBuf& text, bool iTXt) {
   }
 
   DataBuf info;
-  unsigned char unhex[103] = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  0,  0,  0,  0,  0, 0,
-                              0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  0,  0,  0,  1,  2, 3,
-                              4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  0,  0,  0,  0,  0, 0,
-                              0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 11, 12, 13, 14, 15};
+  const unsigned char unhex[103] = {
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,  0,  0,  0,  0,  0,  0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 0, 0, 0, 0, 0,  0,  0,  0,  0,  0,  0, 0,
+      0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 10, 11, 12, 13, 14, 15,
+  };
 
   if (iTXt) {
     info.alloc(text.size());
@@ -581,7 +582,7 @@ DataBuf PngChunk::readRawProfile(const DataBuf& text, bool iTXt) {
 }  // PngChunk::readRawProfile
 
 std::string PngChunk::writeRawProfile(const std::string& profileData, const char* profileType) {
-  static byte hex[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
+  static const byte hex[16] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f'};
 
   std::ostringstream oss;
   oss << '\n' << profileType << '\n' << std::setw(8) << profileData.size();