diff --git a/math.c b/math.c
index efe46b3..ea2c63f 100644
--- a/math.c
+++ b/math.c
@@ -149,6 +149,13 @@ fn u64 u64SafeMul(u64 x, u64 y) {
 fn f32 f32FromString(String s) {
   f32 result = 0.0f;
   if (s.length == 0) { return result; }
+  // TODO handle +/- for sign
+  /*
+   * while (*s == ' ') s++;
+    float sign = 1.0f;
+    if (*s == '-') { sign = -1.0f; s++; }
+    else if (*s == '+') s++;
+   * */
   ptr c = s.bytes;
   while (*c >= '0' && *c <= '9') {
     result = result * 10.0f + (*c++ - '0');
diff --git a/string.c b/string.c
index dc5cf78..dba0eae 100644
--- a/string.c
+++ b/string.c
@@ -494,7 +494,11 @@ fn bool stringInsertBytesAtMaybeAlloc(Arena* a, String* s, str bytes, u32 at) {
   bool is_already_enough_space = stringInsertBytesAt(s, bytes, at);
   if (!is_already_enough_space) {
     ptr old_bytes = s->bytes;
-    s->bytes = arenaAllocZero(a, s->capacity + 64);
+    u32 len = strlen(bytes);
+    u32 available_cap = s->capacity - s->length;
+    assert(len > available_cap);
+    s->capacity += (len - available_cap);
+    s->bytes = arenaAllocZero(a, s->capacity);
     MemoryCopy(s->bytes, old_bytes, s->length);
     return stringInsertBytesAt(s, bytes, at);
   }