diff --git a/eeschema/sch_plugins/altium/altium_parser_sch.cpp b/eeschema/sch_plugins/altium/altium_parser_sch.cpp
index cadef57b78..a6b4022d71 100644
--- a/eeschema/sch_plugins/altium/altium_parser_sch.cpp
+++ b/eeschema/sch_plugins/altium/altium_parser_sch.cpp
@@ -43,7 +43,12 @@ ALTIUM_SCH_RECORD ReadRecord( const std::map<wxString, wxString>& aProps )
 
 constexpr int Altium2KiCadUnit( const int val, const int frac )
 {
-    return Mils2iu( val ) * 10 + Mils2iu( frac ) / 10000; // TODO: correct, rounding issues?
+    constexpr double int_limit = ( std::numeric_limits<int>::max() - 10 ) / 2.54;
+
+    double dbase = 10 * Mils2iu( val );
+    double dfrac = Mils2iu( frac ) / 10000.0;
+
+    return KiROUND( Clamp<double>( -int_limit, ( dbase + dfrac ) / 10.0, int_limit ) ) * 10;
 }
 
 
diff --git a/libs/kimath/include/math/util.h b/libs/kimath/include/math/util.h
index 9ec90a892b..958e1e9fb8 100644
--- a/libs/kimath/include/math/util.h
+++ b/libs/kimath/include/math/util.h
@@ -56,7 +56,7 @@ void kimathLogDebug( const char* aFormatString, ... );
  * result is:  lower <= value <= upper
  *</p>
  */
-template <typename T> inline const T& Clamp( const T& lower, const T& value, const T& upper )
+template <typename T> inline constexpr T Clamp( const T& lower, const T& value, const T& upper )
 {
     if( value < lower )
         return lower;