diff --git a/src/cli/cli.cpp b/src/cli/cli.cpp
index 712c82716..84fa9ef06 100644
--- a/src/cli/cli.cpp
+++ b/src/cli/cli.cpp
@@ -1007,6 +1007,7 @@ void Interpreter::ProcessLinkQuality(int argc, char *argv[])
     uint8_t linkQuality;
     long value;
 
+    VerifyOrExit(argc > 0, error = kThreadError_InvalidArgs);
     VerifyOrExit(Hex2Bin(argv[0], extAddress, OT_EXT_ADDRESS_SIZE) >= 0, error = kThreadError_Parse);
 
     if (argc == 1)