diff --git a/lib/strcase.c b/lib/strcase.c
index a89471225..a309e3529 100644
--- a/lib/strcase.c
+++ b/lib/strcase.c
@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -26,6 +26,8 @@
 
 #include "strcase.h"
 
+static char raw_tolower(char in);
+
 /* Portable, consistent toupper (remember EBCDIC). Do not use toupper() because
    its behavior is altered by the current locale. */
 char Curl_raw_toupper(char in)
@@ -96,7 +98,7 @@ char Curl_raw_toupper(char in)
 
 /* Portable, consistent tolower (remember EBCDIC). Do not use tolower() because
    its behavior is altered by the current locale. */
-char Curl_raw_tolower(char in)
+static char raw_tolower(char in)
 {
 #if !defined(CURL_DOES_CONVERSIONS)
   if(in >= 'A' && in <= 'Z')
@@ -245,7 +247,7 @@ void Curl_strntolower(char *dest, const char *src, size_t n)
     return;
 
   do {
-    *dest++ = Curl_raw_tolower(*src);
+    *dest++ = raw_tolower(*src);
   } while(*src++ && --n);
 }
 
diff --git a/lib/strcase.h b/lib/strcase.h
index baa768b2b..cd4c4191a 100644
--- a/lib/strcase.h
+++ b/lib/strcase.h
@@ -7,7 +7,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -40,7 +40,6 @@ int Curl_safe_strcasecompare(const char *first, const char *second);
 int Curl_strncasecompare(const char *first, const char *second, size_t max);
 
 char Curl_raw_toupper(char in);
-char Curl_raw_tolower(char in);
 
 /* checkprefix() is a shorter version of the above, used when the first
    argument is zero-byte terminated */