Fix minor typo.

Author: yuvallanger

srfi-64-1.6.html

@@ -275,7 +275,7 @@ <h3>Tests for catching errors</h3>
 <h3>Testing syntax</h3>
 <p>
 Testing syntax is tricky, especially if we want to
-check that invalid syntax is causes an error.
+check that invalid syntax is causing an error.
 The following utility function can help:</p>
 <pre>
 (<b>test-read-eval-string</b> <var>string</var>)

srfi-64.html

@@ -221,7 +221,7 @@ <h4>Tests for catching errors</h4>
 <h4>Testing syntax</h4>
 <p>
 Testing syntax is tricky, especially if we want to
-check that invalid syntax is causes an error.
+check that invalid syntax is causing an error.
 The following utility function can help:</p>
 <pre>
 (<b>test-read-eval-string</b> <var>string</var>)