diff --git a/src/meshTools/octree/octreeDataPoint.H b/src/meshTools/octree/octreeDataPoint.H
index 32e4709734..8435b59886 100644
--- a/src/meshTools/octree/octreeDataPoint.H
+++ b/src/meshTools/octree/octreeDataPoint.H
@@ -69,7 +69,7 @@ public:
     // Constructors
 
         //- Construct from components. Holds reference to points!
-        octreeDataPoint(const pointField&);
+        explicit octreeDataPoint(const pointField&);
 
 
     // Member Functions
diff --git a/src/meshTools/octree/treeBoundBox.H b/src/meshTools/octree/treeBoundBox.H
index 01660d618d..a0fa8a1f51 100644
--- a/src/meshTools/octree/treeBoundBox.H
+++ b/src/meshTools/octree/treeBoundBox.H
@@ -170,11 +170,11 @@ public:
         inline treeBoundBox(const point& min, const point& max);
 
         //- Construct from components
-        inline treeBoundBox(const boundBox& bb);
+        explicit inline treeBoundBox(const boundBox& bb);
 
         //- Construct as the bounding box of the given pointField.
         //  Local processor domain only (no reduce as in boundBox)
-        treeBoundBox(const UList<point>&);
+        explicit treeBoundBox(const UList<point>&);
 
         //- Construct as subset of points
         //  Local processor domain only (no reduce as in boundBox)