diff --git a/lib/Tapir/Parser.pir b/lib/Tapir/Parser.pir
index 3ea9ee1..dfe0340 100644
--- a/lib/Tapir/Parser.pir
+++ b/lib/Tapir/Parser.pir
@@ -113,11 +113,13 @@ Written and maintained by Jonathan "Duke" Leto C<< jonathan@leto.net >>.
 
 .sub is_tap :method
     .param string tapline
-    $S0 = substr tapline, 0, 2
-    if $S0 == "ok" goto yes
+    $S0 = substr tapline, 0, 3
+    if $S0 == "ok " goto yes
 
-    $S0 = substr tapline, 0, 5
-    if $S0 == "not ok" goto yes
+    $S0 = substr tapline, 0, 7
+    if $S0 == "not ok " goto yes
+
+    goto no
     yes:
         .return( 1 )
     no:
diff --git a/t/03-parse_tapstream_error.t b/t/03-parse_tapstream_error.t
index d5973ff..98fcb4d 100755
--- a/t/03-parse_tapstream_error.t
+++ b/t/03-parse_tapstream_error.t
@@ -7,7 +7,7 @@
     load_bytecode 'lib/Tapir/Stream.pbc'
     load_bytecode 'lib/Tapir/Parser.pbc'
 
-    plan(35)
+    plan(42)
 
     # setup test data
     klass = newclass [ 'Tapir'; 'Parser' ]
@@ -19,6 +19,36 @@
     test_exit_code(tapir)
     test_exit_code_pass(tapir)
     test_parse_tapstream_out_of_order(tapir)
+    test_is_tap(tapir)
+.end
+
+.sub test_is_tap
+    .param pmc tapir
+    .local pmc stream
+
+    $S0 = 'Who paid for this damn Bail out!?!'
+    $I0 = tapir.'is_tap'($S0)
+    is($I0,0,'invalid bailout detected by is_tap')
+
+    $S0 = 'ok 42'
+    $I0 = tapir.'is_tap'($S0)
+    is($I0,1,'valid ok line detected by is_tap')
+
+    $S0 = 'not ok 99999'
+    $I0 = tapir.'is_tap'($S0)
+    is($I0,1,'valid not ok line detected by is_tap')
+
+    $S0 = 'Some junk # and a comment'
+    $I0 = tapir.'is_tap'($S0)
+    is($I0,0,'non-TAP lines properly detected by is_tap')
+
+    $S0 = 'okie dokey pokey'
+    $I0 = tapir.'is_tap'($S0)
+    is($I0,0,'non-TAP lines properly detected by is_tap')
+
+    $S0 = 'not oklahoma, but any other state!'
+    $I0 = tapir.'is_tap'($S0)
+    is($I0,0,'non-TAP lines properly detected by is_tap')
 .end
 
 .sub test_parse_tapstream_out_of_order