diff --git a/src/conversion/ensight/file/ensightFile.C b/src/conversion/ensight/file/ensightFile.C
index 46809d4ebe..841c017f0f 100644
--- a/src/conversion/ensight/file/ensightFile.C
+++ b/src/conversion/ensight/file/ensightFile.C
@@ -282,14 +282,15 @@ Foam::Ostream& Foam::ensightFile::writeKeyword(const keyType& key)
 {
     if (allowUndef_)
     {
-        write(string(key + " undef"));
+        write(string(static_cast<const string&>(key) + " undef"));
         newline();
         write(undefValue_);
         newline();
     }
     else
     {
-        write(key);
+        // ensure we get ensightFile::write(const string&)
+        write(static_cast<const string&>(key));
         newline();
     }
     return *this;
diff --git a/src/conversion/ensight/file/ensightGeoFile.C b/src/conversion/ensight/file/ensightGeoFile.C
index 214a882a5e..c52aa79356 100644
--- a/src/conversion/ensight/file/ensightGeoFile.C
+++ b/src/conversion/ensight/file/ensightGeoFile.C
@@ -74,7 +74,8 @@ Foam::ensightGeoFile::~ensightGeoFile()
 
 Foam::Ostream& Foam::ensightGeoFile::writeKeyword(const keyType& key)
 {
-    write(key); newline();
+    // ensure we get ensightFile::write(const string&)
+    write(static_cast<const string&>(key)); newline();
 
     return *this;
 }