diff --git a/libs/libc/stdlib/lib_checkbase.c b/libs/libc/stdlib/lib_checkbase.c
index c70c436cf2..ad8f112680 100644
--- a/libs/libc/stdlib/lib_checkbase.c
+++ b/libs/libc/stdlib/lib_checkbase.c
@@ -69,21 +69,21 @@ int lib_checkbase(int base, FAR const char **pptr)
 
       if (*ptr == '0')
         {
-          if (ptr[1] != '\0')
-            {
-              /* Assume octal */
+          /* Assume octal */
 
+          if (lib_isbasedigit(ptr[1], 8, NULL))
+            {
               base = 8;
               ptr++;
+            }
 
-              /* Check for hexadecimal */
+          /* Check for hexadecimal */
 
-              if ((*ptr == 'X' || *ptr == 'x') &&
-                  lib_isbasedigit(ptr[1], 16, NULL))
-                {
-                  base = 16;
-                  ptr++;
-                }
+          else if ((ptr[1] == 'X' || ptr[1] == 'x') &&
+                   lib_isbasedigit(ptr[2], 16, NULL))
+            {
+              base = 16;
+              ptr += 2;
             }
         }
     }