diff --git a/tools/psl.c b/tools/psl.c
index ff28285..7d5db0c 100644
--- a/tools/psl.c
+++ b/tools/psl.c
@@ -73,6 +73,10 @@ int main(int argc, const char *const *argv)
 	const char *const *arg, *psl_file = NULL, *cookie_domain = NULL;
 	psl_ctx_t *psl = (psl_ctx_t *) psl_builtin();
 
+	/* set current locale according to the environment variables */
+	#include <locale.h>
+	setlocale(LC_ALL, "");
+
 	for (arg = argv + 1; arg < argv + argc; arg++) {
 		if (!strncmp(*arg, "--", 2)) {
 			if (!strcmp(*arg, "--is-public-suffix"))
@@ -137,33 +141,41 @@ int main(int argc, const char *const *argv)
 			exit(2);
 		}
 		if (arg >= argv + argc) {
-			if (isatty(STDIN_FILENO)) {
-				char buf[256], *domain;
-				size_t len;
+			char buf[256], *domain, *lower;
+			size_t len;
+			int rc;
 
-				// read URLs from STDIN
-				while (fgets(buf, sizeof(buf), stdin)) {
-					for (domain = buf; isspace(*domain); domain++); // skip leading spaces
-					if (*domain == '#' || !*domain) continue; // skip empty lines and comments
-					for (len = strlen(domain); len && isspace(domain[len - 1]); len--);  // skip trailing spaces
-					domain[len] = 0;
+			// read URLs from STDIN
+			while (fgets(buf, sizeof(buf), stdin)) {
+				for (domain = buf; isspace(*domain); domain++); // skip leading spaces
+				if (*domain == '#' || !*domain) continue; // skip empty lines and comments
+				for (len = strlen(domain); len && isspace(domain[len - 1]); len--);  // skip trailing spaces
+				domain[len] = 0;
 
-					if (mode == 1)
-						printf("%s: %d\n", domain, psl_is_public_suffix(psl, domain));
-					else if (mode == 2)
-						printf("%s: %s\n", domain, psl_unregistrable_domain(psl, domain));
-					else if (mode == 3)
-						printf("%s: %s\n", domain, psl_registrable_domain(psl, domain));
-					else if (mode == 4)
-						printf("%s: %d\n", domain, psl_is_cookie_domain_acceptable(psl, domain, cookie_domain));
+				if ((rc = psl_str_to_utf8lower(domain, NULL, NULL, &lower)) != 0)
+					fprintf(stderr, "%s: Failed to convert to lowercase UTF-8 (%d)\n", domain, rc);
+				else if (mode == 1)
+					printf("%s: %d (%s)\n", domain, psl_is_public_suffix(psl, lower), lower);
+				else if (mode == 2)
+					printf("%s: %s\n", domain, psl_unregistrable_domain(psl, lower));
+				else if (mode == 3)
+					printf("%s: %s\n", domain, psl_registrable_domain(psl, lower));
+				else if (mode == 4) {
+					char *cookie_domain_lower;
+
+					if ((rc = psl_str_to_utf8lower(domain, NULL, NULL, &cookie_domain_lower)) != 0)
+						fprintf(stderr, "%s: Failed to convert cookie domain '%s' to lowercase UTF-8 (%d)\n", domain, cookie_domain, rc);
+					else
+						printf("%s: %d\n", domain, psl_is_cookie_domain_acceptable(psl, lower, cookie_domain));
+
+					free(cookie_domain_lower);
 				}
 
-				psl_free(psl);
-				exit(0);
-			} else {
-				fprintf(stderr, "No domains given - aborting\n");
-				exit(3);
+				free(lower);
 			}
+
+			psl_free(psl);
+			exit(0);
 		}
 	}
 
@@ -199,6 +211,13 @@ int main(int argc, const char *const *argv)
 			printf("builtin compile time: %ld (%s)\n", psl_builtin_compile_time(), time2str(psl_builtin_compile_time()));
 			printf("builtin file time: %ld (%s)\n", psl_builtin_file_time(), time2str(psl_builtin_file_time()));
 			printf("builtin SHA1 file hash: %s\n", psl_builtin_sha1sum());
+
+#ifdef WITH_LIBICU
+			#include <unicode/uloc.h>
+			#include <unicode/ucnv.h>
+			printf("uloc_getDefault=%s\n", uloc_getDefault());
+			printf("ucnv_getDefaultName=%s\n", ucnv_getDefaultName());
+#endif
 		} else
 			printf("No builtin PSL data available\n");
 	}