diff --git a/src/internal.c b/src/internal.c
index 067a0e75c..e43d35820 100644
--- a/src/internal.c
+++ b/src/internal.c
@@ -3837,18 +3837,19 @@ static int MatchDomainName(const char* pattern, int len, const char* str)
 
     while (len > 0) {
 
-        p = (char)XTOLOWER(*pattern++);
+        p = (char)XTOLOWER((unsigned char)*pattern++);
         if (p == 0)
             break;
 
         if (p == '*') {
-            while (--len > 0 && (p = (char)XTOLOWER(*pattern++)) == '*')
+            while (--len > 0 && 
+                         (p = (char)XTOLOWER((unsigned char)*pattern++)) == '*')
                 ;
 
             if (len == 0)
                 p = '\0';
 
-            while ( (s = (char)XTOLOWER(*str)) != '\0') {
+            while ( (s = (char)XTOLOWER((unsigned char) *str)) != '\0') {
                 if (s == p)
                     break;
                 if (s == '.')
@@ -3857,7 +3858,7 @@ static int MatchDomainName(const char* pattern, int len, const char* str)
             }
         }
         else {
-            if (p != (char)XTOLOWER(*str))
+            if (p != (char)XTOLOWER((unsigned char) *str))
                 return 0;
         }
 
diff --git a/wolfcrypt/src/asn.c b/wolfcrypt/src/asn.c
index 9c79e13de..094629c6d 100644
--- a/wolfcrypt/src/asn.c
+++ b/wolfcrypt/src/asn.c
@@ -3238,7 +3238,8 @@ static int MatchBaseName(int type, const char* name, int nameSz,
     }
 
     while (nameSz > 0) {
-        if (XTOLOWER(*name++) != XTOLOWER(*base++))
+        if (XTOLOWER((unsigned char)*name++) != 
+                                               XTOLOWER((unsigned char)*base++))
             return 0;
         nameSz--;
     }
diff --git a/wolfssl/wolfcrypt/types.h b/wolfssl/wolfcrypt/types.h
index 51a8d5f63..d729ce31b 100644
--- a/wolfssl/wolfcrypt/types.h
+++ b/wolfssl/wolfcrypt/types.h
@@ -217,11 +217,6 @@
 	        #define XISALPHA(c)     isalpha((c))
 	    #endif
 	    /* needed by wolfSSL_check_domain_name() */
-	    #ifdef __CYGWIN__
-	        /* Cygwin uses a macro version of tolower() by default, use the
-	         * function version. */
-	        #undef tolower
-	    #endif
 	    #define XTOLOWER(c)      tolower((c))
 	#endif