diff --git a/include/cling/Interpreter/MultiplexExternalSemaSource.h b/include/cling/Interpreter/MultiplexExternalSemaSource.h
index d6b4175c..81518a76 100644
--- a/include/cling/Interpreter/MultiplexExternalSemaSource.h
+++ b/include/cling/Interpreter/MultiplexExternalSemaSource.h
@@ -10,6 +10,7 @@
 #include "clang/Sema/ExternalSemaSource.h"
 #include "clang/Sema/Weak.h"
 
+#include "llvm/ADT/ArrayRef.h"
 #include "llvm/ADT/SmallVector.h"
 
 #include <utility>
@@ -36,10 +37,15 @@ namespace cling {
 class MultiplexExternalSemaSource : public clang::ExternalSemaSource {
 
 private:
-  llvm::SmallVector<ExternalSemaSource*, 4> m_Sources;
+  llvm::SmallVector<ExternalSemaSource*, 4> m_Sources; // doesn't own them.
 
 public:
-  MultiplexExternalSemaSource() { }
+
+  ///\brief Constructs the external source with given elements.
+  ///
+  ///\param[in] sources - Array of ExternalSemaSources.
+  ///
+  MultiplexExternalSemaSource(llvm::ArrayRef<ExternalSemaSource*> sources);
 
   ~MultiplexExternalSemaSource();
 
diff --git a/lib/Interpreter/MultiplexExternalSemaSource.cpp b/lib/Interpreter/MultiplexExternalSemaSource.cpp
index ce84b28a..75e53e08 100644
--- a/lib/Interpreter/MultiplexExternalSemaSource.cpp
+++ b/lib/Interpreter/MultiplexExternalSemaSource.cpp
@@ -11,6 +11,13 @@
 using namespace clang;
 
 namespace cling {
+  MultiplexExternalSemaSource::MultiplexExternalSemaSource(
+                                   llvm::ArrayRef<ExternalSemaSource*> sources) {
+    for (size_t i = 0; i < sources.size(); ++i)
+      m_Sources.push_back(sources[i]);
+  }
+
+
   // pin the vtable here.
   MultiplexExternalSemaSource::~MultiplexExternalSemaSource() {}