diff --git a/src/gtk/webview_webkit2.cpp b/src/gtk/webview_webkit2.cpp
index a8c8cb1280..59fa602c63 100644
--- a/src/gtk/webview_webkit2.cpp
+++ b/src/gtk/webview_webkit2.cpp
@@ -1141,7 +1141,8 @@ bool wxWebViewWebKit::RunScriptSync(const wxString& javascript, wxString* output
 
     if ( !js_result )
     {
-        wxLogWarning(_("Error running JavaScript: %s"), error.GetMessage());
+        if ( output )
+            *output = error.GetMessage();
         return false;
     }
 
@@ -1158,8 +1159,11 @@ bool wxWebViewWebKit::RunScriptSync(const wxString& javascript, wxString* output
 
     if ( exception )
     {
-        wxJSStringRef ex_value(JSValueToStringCopy(context, exception, NULL));
-        wxLogWarning(_("Exception running JavaScript: %s"), ex_value.ToWxString());
+        if ( output )
+        {
+            wxJSStringRef ex_value(JSValueToStringCopy(context, exception, NULL));
+            *output = ex_value.ToWxString();
+        }
 
         return false;
     }
@@ -1172,23 +1176,31 @@ bool wxWebViewWebKit::RunScriptSync(const wxString& javascript, wxString* output
 
 bool wxWebViewWebKit::RunScript(const wxString& javascript, wxString* output)
 {
-    wxCHECK_MSG( m_web_view, false,
-        wxS("wxWebView must be created before calling RunScript()") );
-
     wxJSScriptWrapper wrapJS(javascript, &m_runScriptCount);
 
+    // This string is also used as an error indicator: it's cleared if there is
+    // no error or used in the warning message below if there is one.
     wxString result;
-    bool isValidJS = RunScriptSync(wrapJS.GetWrappedCode(), &result);
-
-    if ( isValidJS && result == "true" )
+    if ( RunScriptSync(wrapJS.GetWrappedCode(), &result)
+            && result == wxS("true") )
     {
-        RunScriptSync(wrapJS.GetOutputCode(), output);
+        if ( RunScriptSync(wrapJS.GetOutputCode(), &result) )
+        {
+            if ( output )
+                *output = result;
+            result.clear();
+        }
+
         RunScriptSync(wrapJS.GetCleanUpCode());
-        return true;
     }
 
-    wxLogWarning(_("JavaScript error: %s"), result);
-    return false;
+    if ( !result.empty() )
+    {
+        wxLogWarning(_("Error running JavaScript: %s"), result);
+        return false;
+    }
+
+    return true;
 }
 
 void wxWebViewWebKit::RegisterHandler(wxSharedPtr<wxWebViewHandler> handler)
diff --git a/src/msw/webview_ie.cpp b/src/msw/webview_ie.cpp
index 66944cab0a..2234f51012 100644
--- a/src/msw/webview_ie.cpp
+++ b/src/msw/webview_ie.cpp
@@ -885,13 +885,7 @@ bool CallEval(const wxString& code,
               wxVariant* varResult)
 {
     wxVariant varCode(code);
-    if ( !scriptAO.Invoke("eval", DISPATCH_METHOD, *varResult, 1, &varCode) )
-    {
-        wxLogWarning(_("Can't run JavaScript"));
-        return false;
-    }
-
-    return true;
+    return scriptAO.Invoke("eval", DISPATCH_METHOD, *varResult, 1, &varCode);
 }
 
 bool wxWebViewIE::RunScript(const wxString& javascript, wxString* output)
@@ -906,7 +900,7 @@ bool wxWebViewIE::RunScript(const wxString& javascript, wxString* output)
     IDispatch* scriptDispatch = NULL;
     if ( FAILED(document->get_Script(&scriptDispatch)) )
     {
-        wxLogWarning(_("Can't get the JavaScript"));
+        wxLogWarning(_("Can't get the JavaScript object"));
         return false;
     }
 
@@ -915,24 +909,35 @@ bool wxWebViewIE::RunScript(const wxString& javascript, wxString* output)
     wxAutomationObject scriptAO(scriptDispatch);
     wxVariant varResult;
 
+    wxString err;
     if ( !CallEval(wrapJS.GetWrappedCode(), scriptAO, &varResult) )
-        return false;
-
-    if ( varResult.IsType("bool") && varResult.GetBool() )
     {
-        if ( !CallEval(wrapJS.GetOutputCode(), scriptAO, &varResult) )
-            return false;
-
+        err = _("failed to evaluate");
+    }
+    else if ( varResult.IsType("bool") && varResult.GetBool() )
+    {
         if ( output != NULL )
-            *output = varResult.MakeString();
+        {
+            if ( CallEval(wrapJS.GetOutputCode(), scriptAO, &varResult) )
+                *output = varResult.MakeString();
+            else
+                err = _("failed to retrieve execution result");
+        }
 
-        if ( !CallEval(wrapJS.GetCleanUpCode(), scriptAO, &varResult) )
-            return false;
-        return true;
+        CallEval(wrapJS.GetCleanUpCode(), scriptAO, &varResult);
+    }
+    else // result available but not the expected "true"
+    {
+        err = varResult.MakeString();
     }
 
-    wxLogWarning(_("JavaScript error: %s"), varResult.MakeString());
-    return false;
+    if ( !err.empty() )
+    {
+        wxLogWarning(_("Error running JavaScript: %s"), varResult.MakeString());
+        return false;
+    }
+
+    return true;
 }
 
 void wxWebViewIE::RegisterHandler(wxSharedPtr<wxWebViewHandler> handler)
diff --git a/src/osx/webview_webkit.mm b/src/osx/webview_webkit.mm
index ea75162a9d..13b76e0626 100644
--- a/src/osx/webview_webkit.mm
+++ b/src/osx/webview_webkit.mm
@@ -417,26 +417,42 @@ bool wxWebViewWebKit::RunScript(const wxString& javascript, wxString* output)
     wxJSScriptWrapper wrapJS(javascript, &m_runScriptCount);
 
     NSString* result = [m_webView stringByEvaluatingJavaScriptFromString:
-                              wxCFStringRef( wrapJS.GetWrappedCode() ).AsNSString()];
+                            wxCFStringRef( wrapJS.GetWrappedCode() ).AsNSString()];
 
-    if ( result != nil && [result isEqualToString:@"true"] )
+    wxString err;
+    if ( result == nil )
+    {
+        // This is not very informative, but we just don't have any other
+        // information in this case.
+        err = _("failed to evaluate");
+    }
+    else if ( [result isEqualToString:@"true"] )
     {
         result = [m_webView stringByEvaluatingJavaScriptFromString:
-                              wxCFStringRef( wrapJS.GetOutputCode() ).AsNSString()];
+                    wxCFStringRef( wrapJS.GetOutputCode() ).AsNSString()];
 
         [m_webView stringByEvaluatingJavaScriptFromString:
-                              wxCFStringRef( wrapJS.GetCleanUpCode() ).
-                              AsNSString()];
+            wxCFStringRef( wrapJS.GetCleanUpCode() ).AsNSString()];
 
-        if ( result != nil && output != NULL )
-            *output = wxCFStringRef::AsString(result);
+        if ( output != NULL )
+        {
+            if ( result )
+                *output = wxCFStringRef::AsString(result);
+            else
+                err = _("failed to retrieve execution result");
+        }
     }
-    else
+    else // result available but not the expected "true"
     {
-        if ( result != nil )
-            wxLogWarning(_("JavaScript error: %s"), wxCFStringRef::AsString(result));
+        err = wxCFStringRef::AsString(result);
+    }
+
+    if ( !err.empty() )
+    {
+        wxLogWarning(_("Error running JavaScript: %s"), err);
         return false;
     }
+
     return true;
 }