diff --git a/newbrt/logger.c b/newbrt/logger.c
index b85ab709b3f..5b1a4c7d804 100644
--- a/newbrt/logger.c
+++ b/newbrt/logger.c
@@ -13,28 +13,17 @@ static int delete_logfile(TOKULOGGER logger, long long index);
 static void grab_output(TOKULOGGER logger, LSN *fsynced_lsn);
 static void release_output(TOKULOGGER logger, LSN fsynced_lsn);
 
-// added for #2424
-static BOOL is_a_logfile(char *name) {
-    int r=0;
-    long long num = 0;
-    int len = strlen(name);
-    char num_str[128];
-    if ( len < 11 ) goto not_logfile;
-    // check 'log'
-    r = strncmp(&name[0], "log", 3);             
-    if (r!=0) goto not_logfile; 
-    // check number
-    r = snprintf(&num_str[0], len-11, "%s", &name[3]);
-    r = sscanf(num_str, "%lld", &num);              
-    if (r!=1) goto not_logfile;
-    // check '.tokulog'
-    r = strncmp(&name[len-8], ".tokulog", 8);    
-    if (r!=0) goto not_logfile;
+// added for #2424, improved for #2521
+static BOOL is_a_logfile (const char *name, long long *number_result) {
+    unsigned long long result;
+    int n;
+    int r = sscanf(name, "log%llu.tokulog%n", &result, &n);
+    if (r!=1 || name[n]!=0) return FALSE;
+    *number_result = result;
     return TRUE;
-not_logfile:
-    return FALSE;
 }
 
+
 int toku_logger_create (TOKULOGGER *resultp) {
     int r;
     TAGMALLOC(TOKULOGGER, result);
@@ -526,12 +515,10 @@ int toku_logger_find_next_unused_log_file(const char *directory, long long *resu
     if (d==0) return errno;
     while ((de=readdir(d))) {
 	if (de==0) return errno;
-	long long thisl;
-        int r = 0;
-        if ( is_a_logfile(de->d_name) ) { // #2424
-            r = sscanf(de->d_name, "log%lld.tokulog", &thisl);
+        long long thisl;
+        if ( is_a_logfile(de->d_name, &thisl) ) {
+            if ((long long)thisl > maxf) maxf = thisl;
         }
-	if (r==1 && thisl>maxf) maxf=thisl; 
     }
     *result=maxf+1;
     int r = closedir(d);
@@ -562,9 +549,7 @@ int toku_logger_find_logfiles (const char *directory, char ***resultp, int *n_lo
     int dirnamelen = strlen(directory);
     while ((de=readdir(d))) {
 	long long thisl;
-        if ( !(is_a_logfile(de->d_name)) ) continue; //#2424: Skip over files that don't match the exact logfile template 
-	int r = sscanf(de->d_name, "log%lld.tokulog", &thisl);
-	if (r!=1) continue; // Skip over non-log files.
+        if ( !(is_a_logfile(de->d_name, &thisl)) ) continue; //#2424: Skip over files that don't match the exact logfile template 
 	if (n_results+1>=result_limit) {
 	    result_limit*=2;
 	    result = toku_realloc(result, result_limit*sizeof(*result));