diff --git a/mozilla/mailnews/addrbook/src/nsVCard.cpp b/mozilla/mailnews/addrbook/src/nsVCard.cpp
index 94b7183fb21..bfc1d4994a4 100644
--- a/mozilla/mailnews/addrbook/src/nsVCard.cpp
+++ b/mozilla/mailnews/addrbook/src/nsVCard.cpp
@@ -1127,9 +1127,9 @@ static int yylex() {
 	    if (lexWithinMode(L_BASE64)) {
 		/* get each char and convert to bin on the fly... */
 		p = lexGetDataFromBase64();
-		yylval.str = p;
-		return STRING;
-		}
+                yylval.str = p;
+                return !p && lexLookahead() == EOF ? 0 : STRING;
+            }
 	    else if (lexWithinMode(L_QUOTED_PRINTABLE)) {
 		p = lexGetQuotedPrintable();
 		}