diff --git a/src/osgPlugins/shp/ESRIShapeParser.cpp b/src/osgPlugins/shp/ESRIShapeParser.cpp
index 5ff41fdcf..299fbe5d2 100644
--- a/src/osgPlugins/shp/ESRIShapeParser.cpp
+++ b/src/osgPlugins/shp/ESRIShapeParser.cpp
@@ -20,9 +20,9 @@ ESRIShapeParser::ESRIShapeParser( const std::string fileName, bool useDouble ):
     if( !fileName.empty() )
     {
 #ifdef WIN32
-        if( (fd = open( fileName.c_str(), O_RDONLY | O_BINARY )) <= 0 )
+        if( (fd = open( fileName.c_str(), O_RDONLY | O_BINARY )) < 0 )
 #else
-        if( (fd = open( fileName.c_str(), O_RDONLY )) <= 0 )
+        if( (fd = open( fileName.c_str(), O_RDONLY )) < 0 )
 #endif
         {
             perror( fileName.c_str() );