diff --git a/src/kmime_headers.h b/src/kmime_headers.h
--- a/src/kmime_headers.h
+++ b/src/kmime_headers.h
@@ -1021,7 +1021,7 @@
     QByteArray subType() const;
 
     /**
-      Sets the mimetype and clears already existing parameters.
+      Sets the mimetype.
       @param mimeType The new mimetype.
     */
     void setMimeType(const QByteArray &mimeType);
diff --git a/src/kmime_headers.cpp b/src/kmime_headers.cpp
--- a/src/kmime_headers.cpp
+++ b/src/kmime_headers.cpp
@@ -1680,7 +1680,6 @@
 void ContentType::setMimeType(const QByteArray & mimeType) {
     Q_D(ContentType);
     d->mimeType = mimeType;
-    Parametrized::clear();
 
     if (isMultipart()) {
         d->category = CCcontainer;