diff --git a/Parser/tokenizer.c b/Parser/tokenizer.c
index 79ed87d..3733f49 100644
--- a/Parser/tokenizer.c
+++ b/Parser/tokenizer.c
@@ -1352,19 +1352,38 @@
 				goto imaginary;
 #endif
 			if (c == 'x' || c == 'X') {
+
 				/* Hex */
+				c = tok_nextc(tok);
+				if (!isxdigit(c)) {
+					tok->done = E_TOKEN;
+					tok_backup(tok, c);
+					return ERRORTOKEN;
+				}
 				do {
 					c = tok_nextc(tok);
 				} while (isxdigit(c));
 			}
                         else if (c == 'o' || c == 'O') {
 				/* Octal */
+				c = tok_nextc(tok);
+				if (c < '0' || c > '8') {
+					tok->done = E_TOKEN;
+					tok_backup(tok, c);
+					return ERRORTOKEN;
+				}
 				do {
 					c = tok_nextc(tok);
 				} while ('0' <= c && c < '8');
 			}
 			else if (c == 'b' || c == 'B') {
 				/* Binary */
+				c = tok_nextc(tok);
+				if (c != '0' && c != '1') {
+					tok->done = E_TOKEN;
+					tok_backup(tok, c);
+					return ERRORTOKEN;
+				}
 				do {
 					c = tok_nextc(tok);
 				} while (c == '0' || c == '1');