diff --git a/eval.c b/eval.c
index 429fee63..61d2a2b7 100644
--- a/eval.c
+++ b/eval.c
@@ -1543,16 +1543,16 @@ sexp sexp_vm (sexp ctx, sexp proc) {
   case OP_NULLP:
     _ARG1 = sexp_make_boolean(sexp_nullp(_ARG1)); break;
   case OP_INTEGERP:
-    _ARG1 = sexp_make_boolean(sexp_integerp(_ARG1)
+    j = sexp_integerp(_ARG1);
 #if USE_BIGNUMS
-                              || sexp_bignump(_ARG1)
+    if (! j) j = sexp_bignump(_ARG1);
 #endif
 #if USE_FLONUMS
-                              || (sexp_flonump(_ARG1)
-                                  && (sexp_flonum_value(_ARG1)
-                                      == trunc(sexp_flonum_value(_ARG1))))
+    if (! j)
+      j = (sexp_flonump(_ARG1)
+           && (sexp_flonum_value(_ARG1) == trunc(sexp_flonum_value(_ARG1))));
 #endif
-                              );
+    _ARG1 = sexp_make_boolean(j);
     break;
   case OP_SYMBOLP:
     _ARG1 = sexp_make_boolean(sexp_symbolp(_ARG1)); break;
diff --git a/mkfile b/mkfile
index 3caba3f9..1c6fb068 100644
--- a/mkfile
+++ b/mkfile
@@ -34,3 +34,6 @@ clean:V:
 install:V: $BIN/$TARG
 	mkdir -p $MODDIR
 	cp init.scm $MODDIR/
+
+test:V:
+	./chibi-scheme tests/r5rs-tests.scm
diff --git a/opt/bignum.c b/opt/bignum.c
index da5bbcbd..35cfec49 100644
--- a/opt/bignum.c
+++ b/opt/bignum.c
@@ -186,6 +186,10 @@ sexp sexp_read_bignum (sexp ctx, sexp in, sexp_uint_t init,
   return sexp_bignum_normalize(res);
 }
 
+#ifdef PLAN9
+#define log2(n) (log(n)/log(2))
+#endif
+
 sexp sexp_write_bignum (sexp ctx, sexp a, sexp out, sexp_uint_t base) {
   int i, str_len, lg_base = trunc(log2(base));
   char *data;