diff --git a/src/mesa/shader/arbprogram.syn b/src/mesa/shader/arbprogram.syn
index 1746a876c30..f3aa1ad7249 100644
--- a/src/mesa/shader/arbprogram.syn
+++ b/src/mesa/shader/arbprogram.syn
@@ -1942,10 +1942,10 @@ stateTexEnvProperty
 fragment program
     <optLegacyTexUnitNum>  ::= ""
                              | "[" <legacyTexUnitNum> "]"
-
-NOTE: <optLegaceTexUnitNum> is not optional.
 */
 optLegacyTexUnitNum
+    optLegacyTexUnitNum_1 .or .true .emit 0x00;
+optLegacyTexUnitNum_1
     lbracket_ne .and legacyTexUnitNum .and rbracket;
 
 /*
diff --git a/src/mesa/shader/arbprogram_syn.h b/src/mesa/shader/arbprogram_syn.h
index 5f3f7d6cf46..3f3ab073cf9 100644
--- a/src/mesa/shader/arbprogram_syn.h
+++ b/src/mesa/shader/arbprogram_syn.h
@@ -926,6 +926,8 @@
 "stateTexEnvProperty\n"
 " \"color\" .emit TEX_ENV_COLOR;\n"
 "optLegacyTexUnitNum\n"
+" optLegacyTexUnitNum_1 .or .true .emit 0x00;\n"
+"optLegacyTexUnitNum_1\n"
 " lbracket_ne .and legacyTexUnitNum .and rbracket;\n"
 "legacyTexUnitNum\n"
 " integer;\n"