diff --git a/testSAX.c b/testSAX.c
index 71686ea..b8db61b 100644
--- a/testSAX.c
+++ b/testSAX.c
@@ -557,8 +557,12 @@
     callbacks++;
     if (quiet)
 	return;
-    fprintf(stdout, "SAX.processingInstruction(%s, %s)\n",
-            (char *) target, (char *) data);
+    if (data != NULL)
+	fprintf(stdout, "SAX.processingInstruction(%s, %s)\n",
+		(char *) target, (char *) data);
+    else
+	fprintf(stdout, "SAX.processingInstruction(%s, NULL)\n",
+		(char *) target);
 }
 
 /**