diff --git a/include/exiv2/metadatum.hpp b/include/exiv2/metadatum.hpp
index 37c3a8e0..53efd85a 100644
--- a/include/exiv2/metadatum.hpp
+++ b/include/exiv2/metadatum.hpp
@@ -226,9 +226,7 @@ namespace Exiv2 {
         /*!
           @brief Return the <EM>n</EM>-th component of the value converted to uint32_t.
          */
-        uint32_t toUint32(long n =0) const {
-            return static_cast<uint32_t>(toInt64(n));
-        }
+        uint32_t toUint32(long n =0) const;
         /*!
           @brief Return the <EM>n</EM>-th component of the value converted to float.
                  The return value is -1 if the value is not set and the behaviour
diff --git a/src/metadatum.cpp b/src/metadatum.cpp
index 9b6f57e6..2a5be1ff 100644
--- a/src/metadatum.cpp
+++ b/src/metadatum.cpp
@@ -42,6 +42,10 @@ namespace Exiv2 {
         return os.str();
     }
 
+    uint32_t Metadatum::toUint32(long n) const {
+        return static_cast<uint32_t>(toInt64(n));
+    }
+
     bool cmpMetadataByTag(const Metadatum& lhs, const Metadatum& rhs)
     {
         return lhs.tag() < rhs.tag();