diff --git a/include/exiv2/asfvideo.hpp b/include/exiv2/asfvideo.hpp
index 62a50063..b9c5f597 100644
--- a/include/exiv2/asfvideo.hpp
+++ b/include/exiv2/asfvideo.hpp
@@ -74,7 +74,9 @@ class EXIV2API AsfVideo : public Image {
     bool operator==(const GUIDTag& other) const;
 
     // Constructor to create a GUID object by passing individual values for each attribute
-    GUIDTag(unsigned int data1, unsigned short data2, unsigned short data3, std::array<byte, 8> data4);
+    constexpr GUIDTag(unsigned int data1, unsigned short data2, unsigned short data3, std::array<byte, 8> data4) :
+        data1_(data1), data2_(data2), data3_(data3), data4_(data4) {
+    }
 
     // Constructor to create a GUID object from a byte array
     explicit GUIDTag(const uint8_t* bytes);
diff --git a/src/asfvideo.cpp b/src/asfvideo.cpp
index aed0ae7f..15d0edc3 100644
--- a/src/asfvideo.cpp
+++ b/src/asfvideo.cpp
@@ -46,10 +46,6 @@ bool AsfVideo::GUIDTag::operator==(const AsfVideo::GUIDTag& other) const {
   return data1_ == other.data1_ && data2_ == other.data2_ && data3_ == other.data3_ && data4_ == other.data4_;
 }
 
-AsfVideo::GUIDTag::GUIDTag(unsigned int data1, unsigned short data2, unsigned short data3, std::array<byte, 8> data4) :
-    data1_(data1), data2_(data2), data3_(data3), data4_(data4) {
-}
-
 AsfVideo::GUIDTag::GUIDTag(const uint8_t* bytes) {
   std::copy_n(bytes, DWORD, reinterpret_cast<uint8_t*>(&data1_));
   std::copy_n(bytes + DWORD, WORD, reinterpret_cast<uint8_t*>(&data2_));
@@ -92,7 +88,7 @@ bool AsfVideo::GUIDTag::operator<(const GUIDTag& other) const {
   return std::lexicographical_compare(data4_.begin(), data4_.end(), other.data4_.begin(), other.data4_.end());
 }
 
-const AsfVideo::GUIDTag Header(0x75B22630, 0x668E, 0x11CF, {0xA6, 0xD9, 0x00, 0xAA, 0x00, 0x62, 0xCE, 0x6C});
+constexpr AsfVideo::GUIDTag Header(0x75B22630, 0x668E, 0x11CF, {0xA6, 0xD9, 0x00, 0xAA, 0x00, 0x62, 0xCE, 0x6C});
 
 const std::map<AsfVideo::GUIDTag, std::string> GUIDReferenceTags = {
     //!< Top-level ASF object GUIDS
diff --git a/unitTests/test_FileIo.cpp b/unitTests/test_FileIo.cpp
index b1f11e02..0bf2fe2f 100644
--- a/unitTests/test_FileIo.cpp
+++ b/unitTests/test_FileIo.cpp
@@ -5,9 +5,8 @@
 using namespace Exiv2;
 
 namespace {
-const std::string testData(TESTDATA_PATH);
-const std::string imagePath(testData + "/DSC_3079.jpg");
-const std::string nonExistingImagePath(testData + "/nonExisting.jpg");
+constexpr auto imagePath = TESTDATA_PATH "/DSC_3079.jpg";
+constexpr auto nonExistingImagePath = TESTDATA_PATH "/nonExisting.jpg";
 }  // namespace
 
 TEST(AFileIO, canBeInstantiatedWithFilePath) {