diff -r 9ed97b511b26 -r 1b03bed31241 src/share/vm/services/diagnosticArgument.cpp
--- a/src/share/vm/services/diagnosticArgument.cpp	Thu Sep 19 11:04:23 2013 -0400
+++ b/src/share/vm/services/diagnosticArgument.cpp	Tue Sep 17 17:16:28 2013 +0200
@@ -61,7 +61,7 @@
 }
 
 void GenDCmdArgument::to_string(char* c, char* buf, size_t len) {
-  jio_snprintf(buf, len, "%s", c);
+  jio_snprintf(buf, len, "%s", (c != NULL) ? c : "");
 }
 
 void GenDCmdArgument::to_string(StringArrayArgument* f, char* buf, size_t len) {