diff --git a/test/basic.js b/test/basic.js
index 95b9bab..c6d6d89 100644
--- a/test/basic.js
+++ b/test/basic.js
@@ -34,7 +34,8 @@ describe('basic', () => {
   });
   it('$version', done => {
     const cxt = lib.init();
-    expect(lib.execute(cxt, Buffer.from(`
+    expect(lib.execute(cxt, Buffer.from(
+`
 $version Generated by VerilatedVcd $end
 $date Wed Sep 18 22:59:07 2019
  $end
@@ -45,12 +46,12 @@ $timescale   1ns $end
     $scope module leaf $end
       $var wire 64 "}> counter [63:0] $end
     $upscope $end
-
-`))).to.eq(1); expect(lib.execute(cxt, Buffer.from(`
-
   $upscope $end
 
-$enddefinitions $end
+  $enddefinitions $end
+`
+))).to.eq(0); expect(lib.execute(cxt, Buffer.from(
+  `
 
 #1
 0"}G
@@ -58,9 +59,9 @@ $enddefinitions $end
 1"}G
 #3
 0"}G
-
-`))).to.eq(1);
-    expect(lib.getError(cxt)).to.eq(1);
+`
+))).to.eq(0);
+    expect(lib.getError(cxt)).to.eq(0);
     // expect(lib.getReason(cxt)).to.eq('Expected simulation command');
     // expect(lib.getCommand(cxt)).to.eq(100);
     done();
diff --git a/vcd.c b/vcd.c
index 2de4a97..59f98ef 100644
--- a/vcd.c
+++ b/vcd.c
@@ -48,7 +48,7 @@
     } \
 }
 
-#define ASSERT_BUFFER(name, var) \
+#define ASSERT_BUFFER(name, var, len) \
     const char * var; \
     size_t len; \
     { \
@@ -81,9 +81,9 @@ METHOD(execute) {
     ASSERT_ARGC(2)
     struct vcd_parser_s *state;
     ASSERT_EXTERNAL(args[0], state)
-    ASSERT_BUFFER(args[1], p)
+    ASSERT_BUFFER(args[1], p, plen)
 
-    const int32_t error = vcd_parser_execute(state, p, NULL);
+    const int32_t error = vcd_parser_execute(state, p, p + plen);
 
     napi_value res;
     ASSERT(res, napi_create_int32(env, error, &res))