diff --git a/ACE/protocols/ace/INet/HTTPS_Context.h b/ACE/protocols/ace/INet/HTTPS_Context.h
index 2b37ac70df975..39817884735ba 100644
--- a/ACE/protocols/ace/INet/HTTPS_Context.h
+++ b/ACE/protocols/ace/INet/HTTPS_Context.h
@@ -48,9 +48,9 @@ namespace ACE
 
               ~Context ();
 
-              operator bool () const;
+              explicit operator bool () const;
 
-              bool operator ! () const;
+              explicit bool operator ! () const;
 
               ACE_SSL_Context& ssl_context ();
 
diff --git a/ACE/protocols/ace/INet/HTTP_Status.h b/ACE/protocols/ace/INet/HTTP_Status.h
index 564a41f26678c..0a1368a5edcf7 100644
--- a/ACE/protocols/ace/INet/HTTP_Status.h
+++ b/ACE/protocols/ace/INet/HTTP_Status.h
@@ -121,10 +121,10 @@ namespace ACE
               bool is_ok () const;
 
               /// Return true in case of a *valid* HTTP status
-              operator bool () const;
+              explicit operator bool () const;
 
               /// Return true if status code == INVALID
-              bool operator !() const;
+              explicit bool operator !() const;
 
               /// Returns an appropriate reason phrase
               static const ACE_CString& get_reason(Code status);
diff --git a/ACE/protocols/ace/INet/URLBase.cpp b/ACE/protocols/ace/INet/URLBase.cpp
index 8814eb94dadc8..06a318283ad89 100644
--- a/ACE/protocols/ace/INet/URLBase.cpp
+++ b/ACE/protocols/ace/INet/URLBase.cpp
@@ -31,7 +31,7 @@ namespace ACE
         return this->request_handler_ == 0 || !this->request_handler_->is_response_ok ();
       }
 
-    URLStream::operator bool ()
+    explicit URLStream::operator bool ()
       {
         return this->request_handler_ != 0 && this->request_handler_->is_response_ok ();
       }
diff --git a/ACE/protocols/ace/INet/URLBase.h b/ACE/protocols/ace/INet/URLBase.h
index e6efb596a92c0..31fce21e431ac 100644
--- a/ACE/protocols/ace/INet/URLBase.h
+++ b/ACE/protocols/ace/INet/URLBase.h
@@ -41,9 +41,9 @@ namespace ACE
               URLStream (const URLStream& url_stream);
               ~URLStream ();
 
-              bool operator ! ();
+              explicit bool operator ! ();
 
-              operator bool ();
+              explicit operator bool ();
 
               std::istream& operator * ();
 
diff --git a/TAO/orbsvcs/orbsvcs/FtRtEvent/EventChannel/Dynamic_Bitset.h b/TAO/orbsvcs/orbsvcs/FtRtEvent/EventChannel/Dynamic_Bitset.h
index cca2468ef847b..8a77691f07a80 100644
--- a/TAO/orbsvcs/orbsvcs/FtRtEvent/EventChannel/Dynamic_Bitset.h
+++ b/TAO/orbsvcs/orbsvcs/FtRtEvent/EventChannel/Dynamic_Bitset.h
@@ -31,7 +31,7 @@ class Dynamic_Bitset
     typedef unsigned size_type;
     reference(Dynamic_Bitset* bitset, size_type bit);
     reference operator = (bool val);
-    operator bool () const;
+    explicit operator bool () const;
   private:
     Dynamic_Bitset* bitset_;
     size_type bit_;