diff --git a/cli/bomtool/main.c b/cli/bomtool/main.c
index 1400e94..a743b14 100644
--- a/cli/bomtool/main.c
+++ b/cli/bomtool/main.c
@@ -309,7 +309,7 @@ main(int argc, char *argv[])
 		if (maximum_package_count > 0 && pkgq.length > maximum_package_count)
 			break;
 
-		while (isspace((unsigned int)package[0]))
+		while (isspace((unsigned char)package[0]))
 			package++;
 
 		/* skip empty packages */
diff --git a/cli/main.c b/cli/main.c
index 6b7e403..2aca647 100644
--- a/cli/main.c
+++ b/cli/main.c
@@ -407,7 +407,8 @@ apply_env(pkgconf_client_t *client, pkgconf_pkg_t *world, void *env_prefix_p, in
 	char workbuf[PKGCONF_ITEM_SIZE];
 
 	for (it = want_env_prefix; *it != '\0'; it++)
-		if (!isalpha(*it) && !isdigit(*it))
+		if (!isalpha((unsigned char)*it) &&
+		    !isdigit((unsigned char)*it))
 			return false;
 
 	snprintf(workbuf, sizeof workbuf, "%s_CFLAGS", want_env_prefix);
@@ -1327,7 +1328,7 @@ cleanup3:
 		if (maximum_package_count > 0 && pkgq.length > maximum_package_count)
 			break;
 
-		while (isspace((unsigned int)package[0]))
+		while (isspace((unsigned char)package[0]))
 			package++;
 
 		/* skip empty packages */
diff --git a/libpkgconf/argvsplit.c b/libpkgconf/argvsplit.c
index b47a3d9..9b98e12 100644
--- a/libpkgconf/argvsplit.c
+++ b/libpkgconf/argvsplit.c
@@ -108,7 +108,7 @@ pkgconf_argv_split(const char *src, int *argc, char ***argv)
 			else
 				*dst_iter++ = *src_iter;
 		}
-		else if (isspace((unsigned int)*src_iter))
+		else if (isspace((unsigned char)*src_iter))
 		{
 			if ((*argv)[argc_count] != NULL)
 			{
diff --git a/libpkgconf/dependency.c b/libpkgconf/dependency.c
index 149d95b..da92c3a 100644
--- a/libpkgconf/dependency.c
+++ b/libpkgconf/dependency.c
@@ -329,11 +329,11 @@ pkgconf_dependency_parse_str(pkgconf_client_t *client, pkgconf_list_t *deplist_h
 			break;
 
 		case INSIDE_MODULE_NAME:
-			if (isspace((unsigned int)*ptr))
+			if (isspace((unsigned char)*ptr))
 			{
 				const char *sptr = ptr;
 
-				while (*sptr && isspace((unsigned int)*sptr))
+				while (*sptr && isspace((unsigned char)*sptr))
 					sptr++;
 
 				if (*sptr == '\0')
@@ -397,7 +397,7 @@ pkgconf_dependency_parse_str(pkgconf_client_t *client, pkgconf_list_t *deplist_h
 			break;
 
 		case AFTER_OPERATOR:
-			if (!isspace((unsigned int)*ptr))
+			if (!isspace((unsigned char)*ptr))
 			{
 				vstart = ptr;
 				state = INSIDE_VERSION;
diff --git a/libpkgconf/libpkgconf.h b/libpkgconf/libpkgconf.h
index e72170a..4f39fe7 100644
--- a/libpkgconf/libpkgconf.h
+++ b/libpkgconf/libpkgconf.h
@@ -249,7 +249,7 @@ PKGCONF_API pkgconf_cross_personality_t *pkgconf_cross_personality_default(void)
 PKGCONF_API pkgconf_cross_personality_t *pkgconf_cross_personality_find(const char *triplet);
 PKGCONF_API void pkgconf_cross_personality_deinit(pkgconf_cross_personality_t *personality);
 
-#define PKGCONF_IS_MODULE_SEPARATOR(c) ((c) == ',' || isspace ((unsigned int)(c)))
+#define PKGCONF_IS_MODULE_SEPARATOR(c) ((c) == ',' || isspace ((unsigned char)(c)))
 #define PKGCONF_IS_OPERATOR_CHAR(c) ((c) == '<' || (c) == '>' || (c) == '!' || (c) == '=')
 
 #define PKGCONF_PKG_PKGF_NONE				0x0000
diff --git a/libpkgconf/parser.c b/libpkgconf/parser.c
index da376c6..f4cf7db 100644
--- a/libpkgconf/parser.c
+++ b/libpkgconf/parser.c
@@ -44,7 +44,7 @@ pkgconf_parser_parse(FILE *f, void *data, const pkgconf_parser_operand_func_t *o
 		lineno++;
 
 		p = readbuf;
-		while (*p && isspace((unsigned int)*p))
+		while (*p && isspace((unsigned char)*p))
 			p++;
 		if (*p && p != readbuf)
 		{
@@ -53,13 +53,14 @@ pkgconf_parser_parse(FILE *f, void *data, const pkgconf_parser_operand_func_t *o
 			warned_key_whitespace = true;
 		}
 		key = p;
-		while (*p && (isalpha((unsigned int)*p) || isdigit((unsigned int)*p) || *p == '_' || *p == '.'))
+		while (*p && (isalpha((unsigned char)*p) || isdigit((unsigned char)*p) || *p == '_' || *p == '.'))
 			p++;
 
-		if (!isalpha((unsigned int)*key) && !isdigit((unsigned int)*p))
+		if (!isalpha((unsigned char)*key) &&
+		    !isdigit((unsigned char)*p))
 			continue;
 
-		while (*p && isspace((unsigned int)*p))
+		while (*p && isspace((unsigned char)*p))
 		{
 			if (!warned_key_whitespace)
 			{
@@ -80,12 +81,12 @@ pkgconf_parser_parse(FILE *f, void *data, const pkgconf_parser_operand_func_t *o
 			p++;
 		}
 
-		while (*p && isspace((unsigned int)*p))
+		while (*p && isspace((unsigned char)*p))
 			p++;
 
 		value = p;
 		p = value + (strlen(value) - 1);
-		while (*p && isspace((unsigned int) *p) && p > value)
+		while (*p && isspace((unsigned char) *p) && p > value)
 		{
 			if (!warned_value_whitespace && op == '=')
 			{
diff --git a/libpkgconf/personality.c b/libpkgconf/personality.c
index 6706416..9f88d0f 100644
--- a/libpkgconf/personality.c
+++ b/libpkgconf/personality.c
@@ -148,7 +148,7 @@ valid_triplet(const char *triplet)
 	const char *c = triplet;
 
 	for (; *c; c++)
-		if (!isalnum(*c) && *c != '-' && *c != '_')
+		if (!isalnum((unsigned char)*c) && *c != '-' && *c != '_')
 			return false;
 
 	return true;
diff --git a/libpkgconf/pkg.c b/libpkgconf/pkg.c
index ad98eb0..40565a4 100644
--- a/libpkgconf/pkg.c
+++ b/libpkgconf/pkg.c
@@ -857,9 +857,9 @@ pkgconf_compare_version(const char *a, const char *b)
 
 	while (*one || *two)
 	{
-		while (*one && !isalnum((unsigned int)*one) && *one != '~')
+		while (*one && !isalnum((unsigned char)*one) && *one != '~')
 			one++;
-		while (*two && !isalnum((unsigned int)*two) && *two != '~')
+		while (*two && !isalnum((unsigned char)*two) && *two != '~')
 			two++;
 
 		if (*one == '~' || *two == '~')
@@ -880,22 +880,22 @@ pkgconf_compare_version(const char *a, const char *b)
 		str1 = one;
 		str2 = two;
 
-		if (isdigit((unsigned int)*str1))
+		if (isdigit((unsigned char)*str1))
 		{
-			while (*str1 && isdigit((unsigned int)*str1))
+			while (*str1 && isdigit((unsigned char)*str1))
 				str1++;
 
-			while (*str2 && isdigit((unsigned int)*str2))
+			while (*str2 && isdigit((unsigned char)*str2))
 				str2++;
 
 			isnum = true;
 		}
 		else
 		{
-			while (*str1 && isalpha((unsigned int)*str1))
+			while (*str1 && isalpha((unsigned char)*str1))
 				str1++;
 
-			while (*str2 && isalpha((unsigned int)*str2))
+			while (*str2 && isalpha((unsigned char)*str2))
 				str2++;
 
 			isnum = false;
diff --git a/libpkgconf/win-dirent.h b/libpkgconf/win-dirent.h
index a2e847a..0734d6d 100644
--- a/libpkgconf/win-dirent.h
+++ b/libpkgconf/win-dirent.h
@@ -912,7 +912,7 @@ static int strverscmp(const char *a, const char *b)
 
 	/* Count backwards and find the leftmost digit */
 	j = i;
-	while (j > 0 && isdigit(a[j-1])) {
+	while (j > 0 && isdigit((unsigned char)a[j-1])) {
 		--j;
 	}
 
@@ -924,23 +924,24 @@ static int strverscmp(const char *a, const char *b)
 		}
 
 		/* String with more digits is smaller, e.g 002 < 01 */
-		if (isdigit(a[j])) {
-			if (!isdigit(b[j])) {
+		if (isdigit((unsigned char)a[j])) {
+			if (!isdigit((unsigned char)b[j])) {
 				return -1;
 			}
-		} else if (isdigit(b[j])) {
+		} else if ((unsigned char)isdigit(b[j])) {
 			return 1;
 		}
-	} else if (isdigit(a[j]) && isdigit(b[j])) {
+	} else if ((unsigned char)isdigit(a[j]) &&
+	    isdigit((unsigned char)b[j])) {
 		/* Numeric comparison */
 		size_t k1 = j;
 		size_t k2 = j;
 
 		/* Compute number of digits in each string */
-		while (isdigit(a[k1])) {
+		while (isdigit((unsigned char)a[k1])) {
 			k1++;
 		}
-		while (isdigit(b[k2])) {
+		while (isdigit((unsigned char)b[k2])) {
 			k2++;
 		}
 
diff --git a/tests/lib1/utf8.pc b/tests/lib1/utf8.pc
new file mode 100644
index 0000000..6507ec0
--- /dev/null
+++ b/tests/lib1/utf8.pc
@@ -0,0 +1,10 @@
+prefix=/tëst
+exec_prefix=${prefix}
+libdir=${prefix}/lib
+includedir=${prefix}/include
+
+Name: utf8
+Description: Library installed in a prefix with UTF-8
+Version: 0
+Libs: -L${libdir} -lutf8
+Cflags: -I${includedir}