diff --git a/src/apply.xsl b/src/apply.xsl
index d7fd6e3..5a2b704 100644
--- a/src/apply.xsl
+++ b/src/apply.xsl
@@ -30,6 +30,8 @@
   xmlns:xs="http://www.w3.org/2001/XMLSchema"
   xmlns:f="http://www.lovullo.com/hoxsl/apply">
 
+<import href="apply/arity.xsl" />
+
 
 <function name="f:apply">
   <param name="fnref" as="element(f:ref)" />
@@ -193,20 +195,4 @@
   </message>
 </template>
 
-
-<!--
-  Attempt to retrieve arity of delayed function
-
-  The input must be a function reference.  If the arity cannot be
-  determined, -1 is returned.
--->
-<function name="f:arity" as="xs:decimal">
-  <param name="fnref" as="element(f:ref)" />
-
-  <sequence select="if ( $fnref/@arity ) then
-                      $fnref/@arity
-                    else
-                      -1" />
-</function>
-
 </stylesheet>
diff --git a/src/apply/arity.xsl b/src/apply/arity.xsl
new file mode 100644
index 0000000..5e9de23
--- /dev/null
+++ b/src/apply/arity.xsl
@@ -0,0 +1,48 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Arity calculations on dynamic and partially applied functions
+
+  Copyright (C) 2014 LoVullo Associates, Inc.
+
+    This file is part of hoxsl.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<stylesheet version="2.0"
+  xmlns="http://www.w3.org/1999/XSL/Transform"
+  xmlns:xs="http://www.w3.org/2001/XMLSchema"
+  xmlns:f="http://www.lovullo.com/hoxsl/apply">
+
+
+
+<!--
+  Attempt to retrieve arity of dynamic function
+
+  The input must be a function reference.  Partially applied function
+  references will have an arity equivalent to the remaining parameters
+  in the original function.
+
+  If the arity cannot be determined, -1 is returned.
+-->
+<function name="f:arity" as="xs:decimal">
+  <param name="fnref" as="element(f:ref)" />
+
+  <sequence select="if ( $fnref/@arity ) then
+                      $fnref/@arity
+                    else
+                      -1" />
+</function>
+
+</stylesheet>
diff --git a/test/apply.xspec b/test/apply.xspec
index 8608775..90e644b 100644
--- a/test/apply.xspec
+++ b/test/apply.xspec
@@ -192,43 +192,4 @@
       </scenario>
     </scenario>
   </scenario>
-
-
-  <scenario label="f:arity">
-    <scenario label="given a proper function reference">
-      <variable name="test-arity"
-                select="5" />
-
-      <!-- test our format directly; do not rely on the
-           apply-gen code -->
-      <variable name="fnref">
-        <f:ref arity="{$test-arity}">
-          <foo:bar />
-        </f:ref>
-      </variable>
-
-      <call function="f:arity">
-        <param name="fnref"
-               select="$fnref" />
-      </call>
-
-      <expect label="provides function arity"
-              test="$x:result = $test-arity" />
-    </scenario>
-
-
-    <scenario label="given a function reference with no defined arity">
-      <variable name="fnref">
-        <f:ref><foo:bar /></f:ref>
-      </variable>
-
-      <call function="f:arity">
-        <param name="fnref"
-               select="$fnref" />
-      </call>
-
-      <expect label="returns -1"
-              test="$x:result = -1" />
-    </scenario>
-  </scenario>
 </description>
diff --git a/test/apply/arity.xspec b/test/apply/arity.xspec
new file mode 100644
index 0000000..bb94b01
--- /dev/null
+++ b/test/apply/arity.xspec
@@ -0,0 +1,68 @@
+<?xml version="1.0" encoding="utf-8"?>
+<!--
+  Tests arity calculations
+
+  Copyright (C) 2014 LoVullo Associates, Inc.
+
+    This file is part of hoxsl.
+
+    This program is free software: you can redistribute it and/or modify
+    it under the terms of the GNU General Public License as published by
+    the Free Software Foundation, either version 3 of the License, or
+    (at your option) any later version.
+
+    This program is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU General Public License for more details.
+
+    You should have received a copy of the GNU General Public License
+    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+-->
+
+<description xmlns="http://www.jenitennison.com/xslt/xspec"
+             xmlns:xsl="http://www.w3.org/1999/XSL/Transform"
+             xmlns:x="http://www.jenitennison.com/xslt/xspec"
+             xmlns:f="http://www.lovullo.com/hoxsl/apply"
+             xmlns:foo="http://www.lovullo.com/_junk"
+             stylesheet="../../src/apply/arity.xsl">
+
+
+  <scenario label="f:arity">
+    <scenario label="given a proper function reference">
+      <variable name="test-arity"
+                select="5" />
+
+      <!-- test our format directly; do not rely on the
+           apply-gen code -->
+      <variable name="fnref">
+        <f:ref arity="{$test-arity}">
+          <foo:bar />
+        </f:ref>
+      </variable>
+
+      <call function="f:arity">
+        <param name="fnref"
+               select="$fnref" />
+      </call>
+
+      <expect label="provides function arity"
+              test="$x:result = $test-arity" />
+    </scenario>
+
+
+    <scenario label="given a function reference with no defined arity">
+      <variable name="fnref">
+        <f:ref><foo:bar /></f:ref>
+      </variable>
+
+      <call function="f:arity">
+        <param name="fnref"
+               select="$fnref" />
+      </call>
+
+      <expect label="returns -1"
+              test="$x:result = -1" />
+    </scenario>
+  </scenario>
+</description>