diff --git a/CMakeLists.txt b/CMakeLists.txt
index e20d00d1..25f74e64 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -815,7 +815,7 @@ CHECK_CXX_SOURCE_COMPILES(
 	#include <memory>
 	struct A { int foo; };
 	int main() {
-		std::shared_ptr <A> a = std::make_shared <A>(a);
+		std::shared_ptr <A> a = std::make_shared <A>();
 		return 0;
 	}
 	"
diff --git a/src/vmime/contentDispositionField.cpp b/src/vmime/contentDispositionField.cpp
index 5a9c1212..33234be8 100644
--- a/src/vmime/contentDispositionField.cpp
+++ b/src/vmime/contentDispositionField.cpp
@@ -42,7 +42,7 @@ contentDispositionField::contentDispositionField(contentDispositionField&)
 
 bool contentDispositionField::hasCreationDate() const
 {
-	return findParameter("creation-date");
+	return bool(findParameter("creation-date"));
 }
 
 
@@ -65,7 +65,7 @@ void contentDispositionField::setCreationDate(const datetime& creationDate)
 
 bool contentDispositionField::hasModificationDate() const
 {
-	return findParameter("modification-date");
+	return bool(findParameter("modification-date"));
 }
 
 
@@ -88,7 +88,7 @@ void contentDispositionField::setModificationDate(const datetime& modificationDa
 
 bool contentDispositionField::hasReadDate() const
 {
-	return findParameter("read-date");
+	return bool(findParameter("read-date"));
 }
 
 
@@ -111,7 +111,7 @@ void contentDispositionField::setReadDate(const datetime& readDate)
 
 bool contentDispositionField::hasFilename() const
 {
-	return findParameter("filename");
+	return bool(findParameter("filename"));
 }
 
 
@@ -134,7 +134,7 @@ void contentDispositionField::setFilename(const word& filename)
 
 bool contentDispositionField::hasSize() const
 {
-	return findParameter("size");
+	return bool(findParameter("size"));
 }
 
 
diff --git a/src/vmime/contentTypeField.cpp b/src/vmime/contentTypeField.cpp
index 9f38294a..c36535f3 100644
--- a/src/vmime/contentTypeField.cpp
+++ b/src/vmime/contentTypeField.cpp
@@ -42,7 +42,7 @@ contentTypeField::contentTypeField(contentTypeField&)
 
 bool contentTypeField::hasBoundary() const
 {
-	return findParameter("boundary");
+	return bool(findParameter("boundary"));
 }
 
 
@@ -65,7 +65,7 @@ void contentTypeField::setBoundary(const string& boundary)
 
 bool contentTypeField::hasCharset() const
 {
-	return findParameter("charset");
+	return bool(findParameter("charset"));
 }
 
 
@@ -88,7 +88,7 @@ void contentTypeField::setCharset(const charset& ch)
 
 bool contentTypeField::hasReportType() const
 {
-	return findParameter("report-type");
+	return bool(findParameter("report-type"));
 }