diff --git a/hw/dmx/glxProxy/glxcmds.c b/hw/dmx/glxProxy/glxcmds.c
index 88cf901f7..f7ae11371 100644
--- a/hw/dmx/glxProxy/glxcmds.c
+++ b/hw/dmx/glxProxy/glxcmds.c
@@ -1536,7 +1536,7 @@ int __glXGetVisualConfigs(__GLXclientState *cl, GLbyte *pc)
     int i, p;
 
     screen = req->screen;
-    if (screen > screenInfo.numScreens) {
+    if (screen >= screenInfo.numScreens) {
 	/* The client library must send a valid screen number. */
 	client->errorValue = screen;
 	return BadValue;
@@ -2685,7 +2685,7 @@ int __glXGetFBConfigs(__GLXclientState *cl, GLbyte *pc)
     int numFBConfigs, i, p;
     __GLXscreenInfo *pGlxScreen;
 
-    if (screen > screenInfo.numScreens) {
+    if (screen >= screenInfo.numScreens) {
 	/* The client library must send a valid screen number. */
 	client->errorValue = screen;
 	return BadValue;
@@ -3107,7 +3107,7 @@ int __glXCreatePbuffer(__GLXclientState *cl, GLbyte *pc)
    /*
     ** Look up screen and FBConfig.
     */
-    if (screen > screenInfo.numScreens) {
+    if (screen >= screenInfo.numScreens) {
         /* The client library must send a valid screen number. */
         client->errorValue = screen;
         return BadValue;
diff --git a/hw/dmx/glxProxy/glxcmdsswap.c b/hw/dmx/glxProxy/glxcmdsswap.c
index 960c60d81..feb70a4cf 100644
--- a/hw/dmx/glxProxy/glxcmdsswap.c
+++ b/hw/dmx/glxProxy/glxcmdsswap.c
@@ -252,7 +252,7 @@ int __glXSwapGetVisualConfigs(__GLXclientState *cl, GLbyte *pc)
 
     __GLX_SWAP_INT(&req->screen);
     screen = req->screen;
-    if (screen > screenInfo.numScreens) {
+    if (screen >= screenInfo.numScreens) {
 	/* The client library must send a valid screen number. */
 	client->errorValue = screen;
 	return BadValue;
diff --git a/hw/kdrive/ephyr/ephyrdriext.c b/hw/kdrive/ephyr/ephyrdriext.c
index ce584b051..050ce6c9a 100644
--- a/hw/kdrive/ephyr/ephyrdriext.c
+++ b/hw/kdrive/ephyr/ephyrdriext.c
@@ -473,7 +473,7 @@ EphyrDuplicateVisual (unsigned int a_screen,
     int i=0 ;
 
     EPHYR_LOG ("enter\n") ; 
-    if (a_screen > screenInfo.numScreens) {
+    if (a_screen >= screenInfo.numScreens) {
         EPHYR_LOG_ERROR ("bad screen number\n") ;
         goto out;
     }