diff --git a/ChangeLog b/ChangeLog
index 0abfa2ac9f..0ceb17d7da 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Sun Dec 27 09:47:20 2015  Masaki Suketa <masaki.suketa@nifty.ne.jp>
+
+	* ext/win32ole/win32ole.c (ole_vstr2wc, ole_variant2val): fix blank
+	  string conversion. 
+	  [Bug #11880]
+	  Thanks Akio Tajima for the patch!
+
 Sun Dec 27 09:34:53 2015  craft4coder  <yooobuntu@163.com>
 
 	* doc/extension.rdoc: [DOC] `nul` should be uppercase.
diff --git a/ext/win32ole/win32ole.c b/ext/win32ole/win32ole.c
index 02ad82b4d4..ac3c2a6a73 100644
--- a/ext/win32ole/win32ole.c
+++ b/ext/win32ole/win32ole.c
@@ -864,6 +864,9 @@ ole_vstr2wc(VALUE vstr)
     /* do not type-conversion here to prevent from other arguments
      * changing (if exist) */
     Check_Type(vstr, T_STRING);
+    if (RSTRING_LEN(vstr) == 0) {
+        return NULL;
+    }
 
     enc = rb_enc_get(vstr);
 
@@ -1571,10 +1574,16 @@ ole_variant2val(VARIANT *pvar)
 
     case VT_BSTR:
     {
-        if(V_ISBYREF(pvar))
-            obj = ole_wc2vstr(*V_BSTRREF(pvar), FALSE);
-        else
-            obj = ole_wc2vstr(V_BSTR(pvar), FALSE);
+        if(V_ISBYREF(pvar)) {
+            obj = (SysStringLen(*V_BSTRREF(pvar)) == 0)
+                ? rb_str_new2("")
+                : ole_wc2vstr(*V_BSTRREF(pvar), FALSE);
+        }
+        else {
+            obj = (SysStringLen(V_BSTR(pvar)) == 0)
+                ? rb_str_new2("")
+                : ole_wc2vstr(V_BSTR(pvar), FALSE);
+        }
         break;
     }