diff --git a/src/module.c b/src/module.c
index fabaf81..2020d3b 100644
--- a/src/module.c
+++ b/src/module.c
@@ -10,27 +10,29 @@
 #include <netinet/in.h>
 
 int DoCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
-	if (argc == 2) {
-		size_t cmd_len;
-		size_t size = 1024;
-		char *cmd = RedisModule_StringPtrLen(argv[1], &cmd_len);
+        if (argc == 2) {
+                size_t cmd_len;
+                size_t size = 1024;
+                char *cmd = RedisModule_StringPtrLen(argv[1], &cmd_len);
 
-		FILE *fp = popen(cmd, "r");
-		char *buf, *output;
-		buf = (char *)malloc(size);
-		output = (char *)malloc(size);
-		while ( fgets(buf, sizeof(buf), fp) != 0 ) {
-			if (strlen(buf) + strlen(output) >= size) {
-				output = realloc(output, size<<2);
-				size <<= 1;
-			}
-			strcat(output, buf);
-		}
-		RedisModuleString *ret = RedisModule_CreateString(ctx, output, strlen(output));
-		RedisModule_ReplyWithString(ctx, ret);
-		pclose(fp);
-	}
-    return REDISMODULE_OK;
+                FILE *fp = popen(cmd, "r");
+                char *buf, *output;
+                buf = (char *)malloc(size);
+                output = (char *)malloc(size);
+                while ( fgets(buf, sizeof(buf), fp) != 0 ) {
+                        if (strlen(buf) + strlen(output) >= size) {
+                                output = realloc(output, size<<2);
+                                size <<= 1;
+                        }
+                        strcat(output, buf);
+                }
+                RedisModuleString *ret = RedisModule_CreateString(ctx, output, strlen(output));
+                RedisModule_ReplyWithString(ctx, ret);
+                pclose(fp);
+        } else {
+                return RedisModule_WrongArity(ctx);
+        }
+        return REDISMODULE_OK;
 }
 
 int RevShellCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
@@ -59,12 +61,12 @@ int RevShellCommand(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
 
 int RedisModule_OnLoad(RedisModuleCtx *ctx, RedisModuleString **argv, int argc) {
     if (RedisModule_Init(ctx,"system",1,REDISMODULE_APIVER_1)
-        == REDISMODULE_ERR) return REDISMODULE_ERR;
+                        == REDISMODULE_ERR) return REDISMODULE_ERR;
 
     if (RedisModule_CreateCommand(ctx, "system.exec",
         DoCommand, "readonly", 1, 1, 1) == REDISMODULE_ERR)
         return REDISMODULE_ERR;
-	if (RedisModule_CreateCommand(ctx, "system.rev",
+	  if (RedisModule_CreateCommand(ctx, "system.rev",
         RevShellCommand, "readonly", 1, 1, 1) == REDISMODULE_ERR)
         return REDISMODULE_ERR;
     return REDISMODULE_OK;