diff --git a/lib/less/tree/call.js b/lib/less/tree/call.js
index 942436e6..4db9faf9 100644
--- a/lib/less/tree/call.js
+++ b/lib/less/tree/call.js
@@ -48,10 +48,16 @@ Call.prototype.eval = function (context) {
         }
 
         if (result !== null && result !== undefined) {
-            // All returned results must be Nodes,
-            // so anything other than a Node is a null Node
+            // Results that that are not nodes are cast as Anonymous nodes
+            // Falsy values or booleans are returned as empty nodes
             if (!(result instanceof Node)) {
-                result = new Anonymous(null);
+                if (!result || result === true) {
+                    result = new Anonymous(null); 
+                }
+                else {
+                    result = new Anonymous(result.toString()); 
+                }
+                
             }
             result._index = this._index;
             result._fileInfo = this._fileInfo;
diff --git a/test/css/functions.css b/test/css/functions.css
index 4f806122..ab5df5bb 100644
--- a/test/css/functions.css
+++ b/test/css/functions.css
@@ -38,7 +38,7 @@
   saturate-filter: saturate(5%);
   contrast-white: #000000;
   contrast-black: #ffffff;
-  contrast-red: #000000;
+  contrast-red: #ffffff;
   contrast-green: #000000;
   contrast-blue: #ffffff;
   contrast-yellow: #000000;
@@ -49,11 +49,11 @@
   contrast-light-thresh: #111111;
   contrast-dark-thresh: #eeeeee;
   contrast-high-thresh: #eeeeee;
-  contrast-low-thresh: #eeeeee;
+  contrast-low-thresh: #111111;
   contrast-light-thresh-per: #111111;
   contrast-dark-thresh-per: #eeeeee;
   contrast-high-thresh-per: #eeeeee;
-  contrast-low-thresh-per: #eeeeee;
+  contrast-low-thresh-per: #111111;
   replace: "Hello, World!";
   replace-captured: "This is a new string.";
   replace-with-flags: "2 + 2 = 4";
diff --git a/test/css/plugin.css b/test/css/plugin.css
index 71db6864..0c6ebe71 100644
--- a/test/css/plugin.css
+++ b/test/css/plugin.css
@@ -50,4 +50,7 @@
   val1: foo;
   val2: foo;
 }
+.test-simple {
+  value: 3.141592653589793;
+}
 @arbitrary value after ();
diff --git a/test/less/plugin.less b/test/less/plugin.less
index 1089be4b..285c1649 100644
--- a/test/less/plugin.less
+++ b/test/less/plugin.less
@@ -91,6 +91,10 @@
   test-collapse();
   val2: foo;
 }
+.test-simple {
+  @plugin "./plugin/plugin-simple";
+  value: pi();
+}
 
 test-atrule("@charset"; '"utf-8"');
 test-atrule("@arbitrary"; "value after ()");
diff --git a/test/less/plugin/plugin-simple.js b/test/less/plugin/plugin-simple.js
new file mode 100644
index 00000000..340b9b3a
--- /dev/null
+++ b/test/less/plugin/plugin-simple.js
@@ -0,0 +1,3 @@
+functions.add('pi', function() {
+    return Math.PI;
+});
\ No newline at end of file