diff --git a/c/cvalues.h b/c/cvalues.h
index 6771323..064b976 100644
--- a/c/cvalues.h
+++ b/c/cvalues.h
@@ -1139,7 +1139,7 @@ static value_t fl_neg(value_t n)
 {
     if (isfixnum(n)) {
         fixnum_t s = fixnum(-numval(n));
-        if (__unlikely(s == n))
+        if (__unlikely(n == (ufixnum_t)s))
             return mk_long(-numval(n));  // negate overflows
         else
             return s;
diff --git a/c/flisp.c b/c/flisp.c
index 149436d..b920d45 100644
--- a/c/flisp.c
+++ b/c/flisp.c
@@ -1490,7 +1490,7 @@ apply_cl_top:
         do_neg:
             if (isfixnum(Stack[SP - 1])) {
                 s = fixnum(-numval(Stack[SP - 1]));
-                if (__unlikely(s == Stack[SP - 1]))
+                if (__unlikely(Stack[SP - 1] == (ufixnum_t)s))
                     Stack[SP - 1] =
                     mk_long(-numval(Stack[SP - 1]));  // negate overflows
                 else
diff --git a/c/ios.c b/c/ios.c
index 793f3fd..baeb4b5 100644
--- a/c/ios.c
+++ b/c/ios.c
@@ -970,7 +970,7 @@ int ios_vprintf(struct ios *s, const char *format, va_list args)
             va_end(al);
             return c;
         }
-        if (c < avail) {
+        if (avail > (size_t)c) {
             s->bpos += (size_t)c;
             _write_update_pos(s);
             // TODO: only works right if newline is at end