diff --git a/src/common/util.c b/src/common/util.c
index 98d6867bc6..82ebfaf0bf 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -337,6 +337,19 @@ tor_strisprint(const char *s)
   return 1;
 }
 
+/** Return 1 if no character in <b>s</b> is uppercase, else return 0.
+ */
+int
+tor_strisnonupper(const char *s)
+{
+  while (*s) {
+    if (! TOR_ISUPPER(*s))
+      return 0;
+    s++;
+  }
+  return 1;
+}
+
 /* Compares the first strlen(s2) characters of s1 with s2.  Returns as for
  * strcmp.
  */
diff --git a/src/common/util.h b/src/common/util.h
index bc21d2051f..fb1534469c 100644
--- a/src/common/util.h
+++ b/src/common/util.h
@@ -97,6 +97,7 @@ extern int dmalloc_free(const char *file, const int line, void *pnt,
 void tor_strlower(char *s);
 void tor_strupper(char *s);
 int tor_strisprint(const char *s);
+int tor_strisnonupper(const char *s);
 int strcmpstart(const char *s1, const char *s2);
 int strcasecmpstart(const char *s1, const char *s2);
 int strcmpend(const char *s1, const char *s2);