diff --git a/nix/parseParamsString.nix b/nix/parseParamsString.nix
new file mode 100644
index 0000000..1807d55
--- /dev/null
+++ b/nix/parseParamsString.nix
@@ -0,0 +1,35 @@
+with builtins;
+let
+  listToAttrs = xs:
+    if length xs == 0
+    then { }
+    else if length xs == 1
+    then throw "parseParamsString: Found an odd number of items: ${head xs}"
+    else { ${head xs} = elemAt xs 1; } // listToAttrs (tail (tail xs));
+
+  stripPat = "[[:space:]]+(.*)";
+
+  stripLeft = string:
+    if match stripPat string != null
+    then head (match stripPat string)
+    else string;
+
+  pat1 = "\"([^\"]+)\"(.*)";
+  
+  pat2 = "([^\"][^[:space:]]*)(.*)";
+
+  go = m: [ (elemAt m 0) ] ++ parse (elemAt m 1);
+
+  parse' = string:
+    if string == ""
+    then [ ]
+    else if match pat1 string != null
+    then go (match pat1 string)
+    else if match pat2 string != null
+    then go (match pat2 string)
+    else throw "Match nothing: ${string}";
+
+  parse = string: parse' (stripLeft string);
+in
+string:
+listToAttrs (parse string)
diff --git a/nix/tangleOrgBabel.nix b/nix/tangleOrgBabel.nix
index 27243e7..340e7a5 100644
--- a/nix/tangleOrgBabel.nix
+++ b/nix/tangleOrgBabel.nix
@@ -12,9 +12,27 @@ let
   blockStartRegexp =
     "[[:space:]]*\#\\+[Bb][Ee][Gg][Ii][Nn]_[Ss][Rr][Cc][[:space:]]+"
     + "(" + (concatStringsSep "|" languages) + ")"
-    + "([[:space:]].*)?";
+    + "(([[:space:]].*)?)";
 
-  isBlockStart = line: match blockStartRegexp line != null;
+  parseParamsString = import ./parseParamsString.nix;
+
+  parseParamsString' = s:
+    if s == null
+    then { }
+    else parseParamsString s;
+
+  checkBlockParams = attrs:
+    foldl' (acc: value: acc && value) true
+      (attrValues
+        (mapAttrs (name: value:
+          if name == ":tangle"
+          then value == "yes"
+          else true
+        ) attrs));
+
+  isBlockStart = line:
+    (match blockStartRegexp line != null)
+    && checkBlockParams (parseParamsString' (elemAt (match blockStartRegexp line) 2));
 
   splitListWith = import ./splitWith.nix;
 
diff --git a/test/test.nix b/test/test.nix
index 24467da..24bdd07 100644
--- a/test/test.nix
+++ b/test/test.nix
@@ -7,6 +7,7 @@ let
   matchOrgTag = import ../nix/matchOrgTag.nix;
   matchOrgHeadline = import ../nix/matchOrgHeadline.nix;
   dropUntil = import ../nix/dropUntil.nix;
+  tangleOrgBabel = import ../nix/tangleOrgBabel.nix;
   lines = filter (s: isString s && s != "") (split "\n" (readFile ./test.org));
 in
 pkgs.lib.runTests {
@@ -39,4 +40,19 @@ pkgs.lib.runTests {
     expr = pkgs.lib.last (select (matchOrgTag "optional") lines);
     expected = "/Zaijian/ means goodbye in Mandarin Chinese.";
   };
+
+  testTangleOrgBabel = {
+    expr = pkgs.lib.pipe (tangleOrgBabel { } (readFile ./testTangle.org)) [
+      (split "\n")
+      (filter isString)
+    ];
+
+    expected = [
+      "Default"
+      "Alternative language name"
+      "Upper case"
+      ":tangle yes"
+      "Extra spaces around params"
+    ];
+  };
 }
diff --git a/test/testTangle.org b/test/testTangle.org
new file mode 100644
index 0000000..f4059f9
--- /dev/null
+++ b/test/testTangle.org
@@ -0,0 +1,31 @@
+#+begin_src
+No language
+#+end_src
+
+#+begin_src emacs-lisp
+Default
+#+end_src
+
+#+begin_src elisp
+Alternative language name
+#+end_src elisp
+
+#+BEGIN_SRC emacs-lisp
+Upper case
+#+END_SRC
+
+#+BEGIN_SRC shell
+Different language
+#+END_SRC
+
+#+begin_src emacs-lisp :tangle yes
+:tangle yes
+#+end_src
+
+#+begin_src emacs-lisp  :tangle yes 
+Extra spaces around params
+#+end_src
+
+#+begin_src emacs-lisp :tangle no
+:tangle no
+#+end_src