diff --git a/ccminer.cpp b/ccminer.cpp
index 41db279..12f61ec 100644
--- a/ccminer.cpp
+++ b/ccminer.cpp
@@ -3593,10 +3593,10 @@ void parse_arg(int key, char *arg)
 		{
 			int device_thr[MAX_GPUS] = { 0 };
 			int ngpus = cuda_num_devices();
-			char * pch = strtok (arg,",");
+			char* pch = strtok(arg,",");
 			opt_n_threads = 0;
 			while (pch != NULL && opt_n_threads < MAX_GPUS) {
-				if (pch[0] >= '0' && pch[0] <= '9' && pch[1] == '\0')
+				if (pch[0] >= '0' && pch[0] <= '9' && strlen(pch) <= 2)
 				{
 					if (atoi(pch) < ngpus)
 						device_map[opt_n_threads++] = atoi(pch);