diff --git a/libs/libc/stdlib/lib_strtoul.c b/libs/libc/stdlib/lib_strtoul.c
index 92f6bcc08c7..3f4959aab79 100644
--- a/libs/libc/stdlib/lib_strtoul.c
+++ b/libs/libc/stdlib/lib_strtoul.c
@@ -103,6 +103,11 @@ unsigned long strtoul(FAR const char *nptr, FAR char **endptr, int base)
               nptr++;
             }
 
+          while (lib_isbasedigit(*nptr, base, &value))
+            {
+              nptr++;
+            }
+
           if (sign == '-')
             {
               accum = (~accum) + 1;
diff --git a/libs/libc/stdlib/lib_strtoull.c b/libs/libc/stdlib/lib_strtoull.c
index 156e557d762..b3b68045163 100644
--- a/libs/libc/stdlib/lib_strtoull.c
+++ b/libs/libc/stdlib/lib_strtoull.c
@@ -107,6 +107,11 @@ unsigned long long strtoull(FAR const char *nptr,
               nptr++;
             }
 
+          while (lib_isbasedigit(*nptr, base, &value))
+            {
+              nptr++;
+            }
+
           if (sign == '-')
             {
               accum = (~accum) + 1;