diff --git a/src/examples/lib.pbl b/src/examples/lib.pbl
index 4f5e7ab..070073a 100644
--- a/src/examples/lib.pbl
+++ b/src/examples/lib.pbl
@@ -22,16 +22,12 @@
 ; Cube a
 (def cube (fn (a) (exp a 3)))
 
-(def fib_ (fn (a depth) (
-  (prnl (cat "n: " a))
+(def fib (fn (a)
   (if (< a 2)
     a
-    (+ (fib_ (- a 1) (+ 1 depth)) (fib_ (- a 2) (+ 1 depth)))
-  )
+    (+ (fib (- a 1)) (fib (- a 2)))
 )))
 
-(def fib (fn (a) ((fib a 0))))
-
 ; Return the larger of the two
 (def max (fn (a b) (if (> a b) a b)))
 
diff --git a/src/examples/pebblisp.pbl b/src/examples/pebblisp.pbl
index 0ad409a..197ed30 100644
--- a/src/examples/pebblisp.pbl
+++ b/src/examples/pebblisp.pbl
@@ -44,7 +44,6 @@
 
 (def first (fn (list) (at 0 list)))
 
-(def up "..")
 (def ~ (env "HOME"))
 
 (def config (cat ~ "/.pebblisp.pbl"))
diff --git a/src/plfunc.c b/src/plfunc.c
index e52d34b..a145e10 100644
--- a/src/plfunc.c
+++ b/src/plfunc.c
@@ -256,9 +256,15 @@ Object substring(Object* params, int length, unused struct Environment* env)
     Object string = params[2];
 
     int len = end.number - start.number;
-    if (len < 0 || start.number >= strlen(string.string)) {
+    size_t stringLen = strlen(string.string);
+    if (len < 0 || start.number > stringLen) {
         return errorWithContext(BAD_PARAMS, string.string);
     }
+
+    if (len > stringLen - start.number) {
+        len = stringLen - start.number;
+    }
+
     Object substr = withLen(len, TYPE_STRING);
     snprintf(substr.string, len + 1, "%s", string.string + start.number);
     return substr;