diff --git a/libs/libc/stdlib/lib_strtod.c b/libs/libc/stdlib/lib_strtod.c
index 57f60787bb..358eb5aec2 100644
--- a/libs/libc/stdlib/lib_strtod.c
+++ b/libs/libc/stdlib/lib_strtod.c
@@ -160,6 +160,7 @@ double strtod(FAR const char *str, FAR char **endptr)
     {
       set_errno(ERANGE);
       number = 0.0;
+      p = (FAR char *)str;
       goto errout;
     }
 
@@ -195,6 +196,14 @@ double strtod(FAR const char *str, FAR char **endptr)
 
       /* Process string of digits */
 
+      if (!isdigit(*p))
+        {
+          set_errno(ERANGE);
+          number = 0.0;
+          p = (FAR char *)str;
+          goto errout;
+        }
+
       n = 0;
       while (isdigit(*p))
         {