diff --git a/scim-wnn/src/scim_wnn_imengine.cpp b/scim-wnn/src/scim_wnn_imengine.cpp
index cc916d5..3db21c3 100644
--- a/scim-wnn/src/scim_wnn_imengine.cpp
+++ b/scim-wnn/src/scim_wnn_imengine.cpp
@@ -556,7 +556,11 @@
     }
 
     wnn.setYomiText(s);
-    wnn.ren_conversion();
+    if (wnn.ren_conversion() == -1) {
+        update_aux_string(utf8_mbstowcs(String(_("could not connect to jserver."))));
+        show_aux_string();
+        return;
+    }
     m_convList = wnn.getConversionList();
     m_conversion = true;
 
diff --git a/scim-wnn/src/wnnconversion.cpp b/scim-wnn/src/wnnconversion.cpp
index ab62e74..704e0f3 100644
--- a/scim-wnn/src/wnnconversion.cpp
+++ b/scim-wnn/src/wnnconversion.cpp
@@ -167,6 +167,7 @@
     m_iconv.convert(y,yomiText);
     strtows(ws,(unsigned char*)y.data());
     bunsetu = jl_ren_conv(wnn,ws,0,-1,WNN_NO_USE);
+    if (bunsetu == -1) return(-1);
     bunList.resize(bunsetu);
     yomiList.resize(bunsetu);
     for(unsigned int i = 0;i < bunsetu;i ++) {