diff --git a/glx/glxdri.c b/glx/glxdri.c
index b3b3e279b..cc6d93976 100644
--- a/glx/glxdri.c
+++ b/glx/glxdri.c
@@ -1136,6 +1136,10 @@ __glXDRIscreenProbe(ScreenPtr pScreen)
 
     __glXScreenInit(&screen->base, pScreen);
 
+    /* The first call simply determines the length of the extension string.
+     * This allows us to allocate some memory to hold the extension string,
+     * but it requires that we call __glXGetExtensionString a second time.
+     */
     buffer_size = __glXGetExtensionString(screen->glx_enable_bits, NULL);
     if (buffer_size > 0) {
 	if (screen->base.GLXextensions != NULL) {
@@ -1150,7 +1154,7 @@ __glXDRIscreenProbe(ScreenPtr pScreen)
     __glXsetEnterLeaveServerFuncs(__glXDRIenterServer, __glXDRIleaveServer);
 
     screen->enterVT = pScrn->EnterVT;
-    pScrn->EnterVT = glxDRIEnterVT; 
+    pScrn->EnterVT = glxDRIEnterVT;
     screen->leaveVT = pScrn->LeaveVT;
     pScrn->LeaveVT = glxDRILeaveVT;
 
diff --git a/glx/glxdri2.c b/glx/glxdri2.c
index 66e08895c..b12293acb 100644
--- a/glx/glxdri2.c
+++ b/glx/glxdri2.c
@@ -583,6 +583,10 @@ __glXDRIscreenProbe(ScreenPtr pScreen)
 
     __glXScreenInit(&screen->base, pScreen);
 
+    /* The first call simply determines the length of the extension string.
+     * This allows us to allocate some memory to hold the extension string,
+     * but it requires that we call __glXGetExtensionString a second time.
+     */
     buffer_size = __glXGetExtensionString(screen->glx_enable_bits, NULL);
     if (buffer_size > 0) {
 	if (screen->base.GLXextensions != NULL) {