diff --git a/src/config_file.c b/src/config_file.c
index d6a62b85c..52a5376bd 100644
--- a/src/config_file.c
+++ b/src/config_file.c
@@ -156,7 +156,7 @@ int git_config_file_normalize_section(char *start, char *end)
 		if (end && scan >= end)
 			break;
 		if (isalnum(*scan))
-			*scan = (char)tolower(*scan);
+			*scan = (char)git__tolower(*scan);
 		else if (*scan != '-' || scan == start)
 			return GIT_EINVALIDSPEC;
 	}
@@ -1083,7 +1083,7 @@ static int parse_section_header(struct reader *reader, char **section_out)
 			goto fail_parse;
 		}
 
-		name[name_length++] = (char) tolower(c);
+		name[name_length++] = (char)git__tolower(c);
 
 	} while ((c = line[pos++]) != ']');
 
diff --git a/src/fnmatch.c b/src/fnmatch.c
index d7899e3e6..a2945b8db 100644
--- a/src/fnmatch.c
+++ b/src/fnmatch.c
@@ -164,8 +164,8 @@ p_fnmatchx(const char *pattern, const char *string, int flags, size_t recurs)
 				default:
 				normal:
 						if (c != *string && !((flags & FNM_CASEFOLD) &&
-									(tolower((unsigned char)c) ==
-									tolower((unsigned char)*string))))
+									(git__tolower((unsigned char)c) ==
+									git__tolower((unsigned char)*string))))
 								return (FNM_NOMATCH);
 						++string;
 						break;
@@ -190,7 +190,7 @@ rangematch(const char *pattern, char test, int flags, char **newp)
 				++pattern;
 
 		if (flags & FNM_CASEFOLD)
-				test = (char)tolower((unsigned char)test);
+				test = (char)git__tolower((unsigned char)test);
 
 		/*
 			* A right bracket shall lose its special meaning and represent
@@ -207,7 +207,7 @@ rangematch(const char *pattern, char test, int flags, char **newp)
 				if (c == '/' && (flags & FNM_PATHNAME))
 						return (RANGE_NOMATCH);
 				if ((flags & FNM_CASEFOLD))
-						c = (char)tolower((unsigned char)c);
+						c = (char)git__tolower((unsigned char)c);
 				if (*pattern == '-'
 					&& (c2 = *(pattern+1)) != EOS && c2 != ']') {
 						pattern += 2;
@@ -216,7 +216,7 @@ rangematch(const char *pattern, char test, int flags, char **newp)
 						if (c2 == EOS)
 								return (RANGE_ERROR);
 						if (flags & FNM_CASEFOLD)
-								c2 = (char)tolower((unsigned char)c2);
+								c2 = (char)git__tolower((unsigned char)c2);
 						if (c <= test && test <= c2)
 								ok = 1;
 				} else if (c == test)
diff --git a/src/iterator.c b/src/iterator.c
index 93303a87d..7807a1636 100644
--- a/src/iterator.c
+++ b/src/iterator.c
@@ -1405,10 +1405,10 @@ GIT_INLINE(bool) workdir_path_is_dotgit(const git_buf *path)
 	if (path->ptr[len - 1] == '/')
 		len--;
 
-	if (tolower(path->ptr[len - 1]) != 't' ||
-		tolower(path->ptr[len - 2]) != 'i' ||
-		tolower(path->ptr[len - 3]) != 'g' ||
-		tolower(path->ptr[len - 4]) != '.')
+	if (git__tolower(path->ptr[len - 1]) != 't' ||
+		git__tolower(path->ptr[len - 2]) != 'i' ||
+		git__tolower(path->ptr[len - 3]) != 'g' ||
+		git__tolower(path->ptr[len - 4]) != '.')
 		return false;
 
 	return (len == 4 || path->ptr[len - 5] == '/');
diff --git a/src/netops.c b/src/netops.c
index 6047cf1ac..5e8075597 100644
--- a/src/netops.c
+++ b/src/netops.c
@@ -84,7 +84,7 @@ void gitno_consume_n(gitno_buffer *buf, size_t cons)
 int gitno__match_host(const char *pattern, const char *host)
 {
 	for (;;) {
-		char c = tolower(*pattern++);
+		char c = git__tolower(*pattern++);
 
 		if (c == '\0')
 			return *host ? -1 : 0;
@@ -102,7 +102,7 @@ int gitno__match_host(const char *pattern, const char *host)
 	 */
 
 			while(*host) {
-				char h = tolower(*host);
+				char h = git__tolower(*host);
 				if (c == h)
 					return gitno__match_host(pattern, host++);
 				if (h == '.')
@@ -112,7 +112,7 @@ int gitno__match_host(const char *pattern, const char *host)
 			return -1;
 		}
 
-		if (c != tolower(*host++))
+		if (c != git__tolower(*host++))
 			return -1;
 	}
 
diff --git a/src/path.c b/src/path.c
index 8f861e68e..02917607a 100644
--- a/src/path.c
+++ b/src/path.c
@@ -1473,7 +1473,7 @@ static int32_t next_hfs_char(const char **in, size_t *len)
 		 * the ASCII range, which is perfectly fine, because the
 		 * git folder name can only be composed of ascii characters
 		 */
-		return tolower(codepoint);
+		return git__tolower(codepoint);
 	}
 	return 0; /* NULL byte -- end of string */
 }
diff --git a/src/util.c b/src/util.c
index 6bb7d03ee..c62826420 100644
--- a/src/util.c
+++ b/src/util.c
@@ -171,9 +171,9 @@ int git__strcmp(const char *a, const char *b)
 
 int git__strcasecmp(const char *a, const char *b)
 {
-	while (*a && *b && tolower(*a) == tolower(*b))
+	while (*a && *b && git__tolower(*a) == git__tolower(*b))
 		++a, ++b;
-	return (tolower(*a) - tolower(*b));
+	return ((unsigned char)git__tolower(*a) - (unsigned char)git__tolower(*b));
 }
 
 int git__strcasesort_cmp(const char *a, const char *b)
@@ -182,7 +182,7 @@ int git__strcasesort_cmp(const char *a, const char *b)
 
 	while (*a && *b) {
 		if (*a != *b) {
-			if (tolower(*a) != tolower(*b))
+			if (git__tolower(*a) != git__tolower(*b))
 				break;
 			/* use case in sort order even if not in equivalence */
 			if (!cmp)
@@ -193,7 +193,7 @@ int git__strcasesort_cmp(const char *a, const char *b)
 	}
 
 	if (*a || *b)
-		return tolower(*a) - tolower(*b);
+		return (unsigned char)git__tolower(*a) - (unsigned char)git__tolower(*b);
 
 	return cmp;
 }
@@ -212,8 +212,8 @@ int git__strncasecmp(const char *a, const char *b, size_t sz)
 	int al, bl;
 
 	do {
-		al = (unsigned char)tolower(*a);
-		bl = (unsigned char)tolower(*b);
+		al = (unsigned char)git__tolower(*a);
+		bl = (unsigned char)git__tolower(*b);
 		++a, ++b;
 	} while (--sz && al && al == bl);
 
@@ -225,7 +225,7 @@ void git__strntolower(char *str, size_t len)
 	size_t i;
 
 	for (i = 0; i < len; ++i) {
-		str[i] = (char) tolower(str[i]);
+		str[i] = (char)git__tolower(str[i]);
 	}
 }
 
@@ -255,8 +255,8 @@ int git__prefixncmp_icase(const char *str, size_t str_n, const char *prefix)
 	int s, p;
 
 	while(str_n--) {
-		s = (unsigned char)tolower(*str++);
-		p = (unsigned char)tolower(*prefix++);
+		s = (unsigned char)git__tolower(*str++);
+		p = (unsigned char)git__tolower(*prefix++);
 
 		if (s != p)
 			return s - p;
diff --git a/src/util.h b/src/util.h
index be6534580..b2abbe6a6 100644
--- a/src/util.h
+++ b/src/util.h
@@ -275,6 +275,15 @@ extern char *git__strsep(char **end, const char *sep);
 extern void git__strntolower(char *str, size_t len);
 extern void git__strtolower(char *str);
 
+#ifdef GIT_WIN32
+GIT_INLINE(int) git__tolower(int c)
+{
+	return (c >= 'A' && c <= 'Z') ? (c + 32) : c;
+}
+#else
+# define git__tolower(a) tolower(a)
+#endif
+
 GIT_INLINE(const char *) git__next_line(const char *s)
 {
 	while (*s && *s != '\n') s++;
diff --git a/tests/core/string.c b/tests/core/string.c
index ec9575685..90e8fa027 100644
--- a/tests/core/string.c
+++ b/tests/core/string.c
@@ -39,3 +39,45 @@ void test_core_string__2(void)
 	cl_assert(git__strcasesort_cmp("BAR", "foo") < 0);
 	cl_assert(git__strcasesort_cmp("fooBar", "foobar") < 0);
 }
+
+void test_core_string__strcmp(void)
+{
+	cl_assert(git__strcmp("", "") == 0);
+	cl_assert(git__strcmp("foo", "foo") == 0);
+	cl_assert(git__strcmp("Foo", "foo") < 0);
+	cl_assert(git__strcmp("foo", "FOO") > 0);
+	cl_assert(git__strcmp("foo", "fOO") > 0);
+
+	cl_assert(strcmp("rt\303\202of", "rt dev\302\266h") > 0);
+	cl_assert(strcmp("e\342\202\254ghi=", "et") > 0);
+	cl_assert(strcmp("rt dev\302\266h", "rt\303\202of") < 0);
+	cl_assert(strcmp("et", "e\342\202\254ghi=") < 0);
+	cl_assert(strcmp("\303\215", "\303\255") < 0);
+
+	cl_assert(git__strcmp("rt\303\202of", "rt dev\302\266h") > 0);
+	cl_assert(git__strcmp("e\342\202\254ghi=", "et") > 0);
+	cl_assert(git__strcmp("rt dev\302\266h", "rt\303\202of") < 0);
+	cl_assert(git__strcmp("et", "e\342\202\254ghi=") < 0);
+	cl_assert(git__strcmp("\303\215", "\303\255") < 0);
+}
+
+void test_core_string__strcasecmp(void)
+{
+	cl_assert(git__strcasecmp("", "") == 0);
+	cl_assert(git__strcasecmp("foo", "foo") == 0);
+	cl_assert(git__strcasecmp("foo", "Foo") == 0);
+	cl_assert(git__strcasecmp("foo", "FOO") == 0);
+	cl_assert(git__strcasecmp("foo", "fOO") == 0);
+
+	cl_assert(strcasecmp("rt\303\202of", "rt dev\302\266h") > 0);
+	cl_assert(strcasecmp("e\342\202\254ghi=", "et") > 0);
+	cl_assert(strcasecmp("rt dev\302\266h", "rt\303\202of") < 0);
+	cl_assert(strcasecmp("et", "e\342\202\254ghi=") < 0);
+	cl_assert(strcasecmp("\303\215", "\303\255") < 0);
+
+	cl_assert(git__strcasecmp("rt\303\202of", "rt dev\302\266h") > 0);
+	cl_assert(git__strcasecmp("e\342\202\254ghi=", "et") > 0);
+	cl_assert(git__strcasecmp("rt dev\302\266h", "rt\303\202of") < 0);
+	cl_assert(git__strcasecmp("et", "e\342\202\254ghi=") < 0);
+	cl_assert(git__strcasecmp("\303\215", "\303\255") < 0);
+}