diff --git a/firmware/hw_layer/mmc_card.cpp b/firmware/hw_layer/mmc_card.cpp
index 7618504f98..23d630a07c 100644
--- a/firmware/hw_layer/mmc_card.cpp
+++ b/firmware/hw_layer/mmc_card.cpp
@@ -207,17 +207,6 @@ static void removeFile(const char *pathx) {
 	unlockSpi();
 }
 
-/*
-** return lower-case of c if upper-case, else c
-*/
-int mytolower(const char c)  {
-
-  if(c<='Z' &&  c>='A') return (c+32);
-  return (c);
-
-}
-
-
 int
     mystrncasecmp(const char *s1, const char *s2, size_t n)
     {
diff --git a/firmware/util/efilib.cpp b/firmware/util/efilib.cpp
index 9047e6bbaf..82ff775bc9 100644
--- a/firmware/util/efilib.cpp
+++ b/firmware/util/efilib.cpp
@@ -250,6 +250,13 @@ bool strEqualCaseInsensitive(const char *str1, const char *str2) {
 	return true;
 }
 
+/*
+** return lower-case of c if upper-case, else c
+*/
+int mytolower(const char c) {
+  return TO_LOWER(c);
+}
+
 bool strEqual(const char *str1, const char *str2) {
 	// todo: there must be a standard function?!
 	int len1 = strlen(str1);