diff --git a/module/language/c99/compiler.mes b/module/language/c99/compiler.mes
index 2b554781..a734c284 100644
--- a/module/language/c99/compiler.mes
+++ b/module/language/c99/compiler.mes
@@ -1073,6 +1073,7 @@
 
 (define (cstring->number s)
   (cond ((string-prefix? "0x" s) (string->number (string-drop s 2) 16))
+        ((string-prefix? "0b" s) (string->number (string-drop s 2) 2))
         ((string-prefix? "0" s) (string->number s 8))
         (else (string->number s))))
 
diff --git a/scaffold/t.c b/scaffold/t.c
index 8ad92369..015c934d 100644
--- a/scaffold/t.c
+++ b/scaffold/t.c
@@ -347,6 +347,15 @@ math_test ()
   puts ("t: 3 != 3\n");
   if ((3 != 3) !=  0) return 1;
 
+  puts ("t: 011 == 15\n");
+  if (011 != 9) return 1;
+
+  puts ("t: 0b11 == 3\n");
+  if (0b11 != 3) return 1;
+
+  puts ("t: 0x11 == 3\n");
+  if (0x11 != 17) return 1;
+
   return array_test (env);
 }