diff --git a/src/tags.cpp b/src/tags.cpp
index 4d610c16..233f6076 100644
--- a/src/tags.cpp
+++ b/src/tags.cpp
@@ -2887,6 +2887,12 @@ namespace Exiv2 {
         return p_->tagInfo_->typeId_;
     }
 
+    uint16_t ExifKey::defaultCount() const
+    {
+        if (p_->tagInfo_ == 0 || p_->tagInfo_->tag_ == 0xffff) return unknownTag.count_;
+        return p_->tagInfo_->count_;
+    }
+
     uint16_t ExifKey::tag() const
     {
         return p_->tag_;
diff --git a/src/tags.hpp b/src/tags.hpp
index aa7aca44..74707ed9 100644
--- a/src/tags.hpp
+++ b/src/tags.hpp
@@ -172,7 +172,7 @@ namespace Exiv2 {
           @throw Error if the key cannot be constructed from the tag and IFD
                  item parameters.
          */
-        ExifKey(const TagInfo& tagInfo);
+        explicit ExifKey(const TagInfo& tagInfo);
         //! Copy constructor
         ExifKey(const ExifKey& rhs);
         //! Destructor
@@ -204,6 +204,8 @@ namespace Exiv2 {
         std::string tagDesc() const;             // Todo: should be in the base class
         //! Return the default type id for this tag.
         TypeId defaultTypeId() const;              // Todo: should be in the base class
+        //! Return the default number of components (not bytes!) this tag has. (0=any, -1=count not known.)
+        uint16_t defaultCount() const;
         virtual uint16_t tag() const;
 
         AutoPtr clone() const;