diff --git a/src/Makefile.am b/src/Makefile.am
index f9dd8ba3..8ea8885d 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -5,5 +5,5 @@ libckpool_la_SOURCES = libckpool.c libckpool.h
 libckpool_la_LIBADD = @PTHREAD_LIBS@ @MATH_LIBS@ @RT_LIBS@ @JANSSON_LIBS@
 
 bin_PROGRAMS = ckpool
-ckpool_SOURCES = ckpool.c ckpool.h
+ckpool_SOURCES = ckpool.c ckpool.h gbt.c gbt.h
 ckpool_LDADD = libckpool.la
diff --git a/src/gbt.c b/src/gbt.c
new file mode 100644
index 00000000..7183221d
--- /dev/null
+++ b/src/gbt.c
@@ -0,0 +1,77 @@
+/*
+ * Copyright 2011-2014 Con Kolivas
+ *
+ * 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.  See COPYING for more details.
+ */
+
+#include "config.h"
+
+#include <string.h>
+
+#include "ckpool.h"
+#include "libckpool.h"
+
+static const char *b58chars = "123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz";
+
+bool validate_address(connsock_t *cs, const char *address)
+{
+	json_t *val, *res_val, *valid_val;
+	char rpc_req[256];
+	bool ret = false;
+	int len, i, j;
+
+	if (unlikely(!address)) {
+		LOGWARNING("Null address passed to validate_address");
+		return ret;
+	}
+	len = strlen(address);
+	if (len < 27 || len > 34) {
+		LOGWARNING("Invalid address length %d passed to validate_address", len);
+		return ret;
+	}
+	for (i = 0; i < len; i++) {
+		char c = address[i];
+		bool found = false;
+
+		for (j = 0; j < 58; j++) {
+			if (c == b58chars[j]) {
+				found = true;
+				break;
+			}
+		}
+		if (!found) {
+			LOGWARNING("Invalid char %.1s passed to validate_address", &c);
+			return ret;
+		}
+	}
+
+	snprintf(rpc_req, 256, "{\"method\": \"validateaddress\", \"params\": [\"%s\"]}\n", address);
+	val = json_rpc_call(cs, rpc_req);
+	if (!val) {
+		LOGERR("Failed to get valid json response to validate_address");
+		return ret;
+	}
+	res_val = json_object_get(val, "result");
+	if (!res_val) {
+		LOGERR("Failed to get result json response to validate_address");
+		goto out;
+	}
+	valid_val = json_object_get(res_val, "isvalid");
+	if (!valid_val) {
+		LOGERR("Failed to get isvalid json response to validate_address");
+		goto out;
+	}
+	if (!json_is_true(valid_val))
+		LOGWARNING("Bitcoin address %s is NOT valid", address);
+	else {
+		LOGDEBUG("Bitcoin address %s IS valid", address);
+		ret = true;
+	}
+out:
+	if (val)
+		json_decref(val);
+	return ret;
+}
diff --git a/src/gbt.h b/src/gbt.h
new file mode 100644
index 00000000..f4a73e67
--- /dev/null
+++ b/src/gbt.h
@@ -0,0 +1,10 @@
+/*
+ * Copyright 2011-2014 Con Kolivas
+ *
+ * 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.  See COPYING for more details.
+ */
+
+bool validate_address(connsock_t *cs, const char *address);
diff --git a/src/libckpool.c b/src/libckpool.c
index 265656ea..92519408 100644
--- a/src/libckpool.c
+++ b/src/libckpool.c
@@ -1119,7 +1119,7 @@ void target_from_diff(uchar *target, double diff)
 
 	if (unlikely(diff == 0.0)) {
 		/* This shouldn't happen but best we check to prevent a crash */
-		memset(target, 0, 32);
+		memset(target, 0xff, 32);
 		return;
 	}