diff --git a/Makefile.am b/Makefile.am
index de35cb02..7cca850f 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -255,6 +255,12 @@ tests_api_test_CFLAGS  = -Isrc/libespeak-ng ${AM_CFLAGS}
 tests_api_test_LDADD   = src/libespeak-ng-test.la
 tests_api_test_SOURCES = tests/api.c
 
+check_PROGRAMS += tests/ieee80.test
+
+tests_ieee80_test_CFLAGS  = -Isrc/libespeak-ng ${AM_CFLAGS}
+tests_ieee80_test_LDADD   = src/libespeak-ng-test.la
+tests_ieee80_test_SOURCES = tests/ieee80.c
+
 .test.check:
 	@echo "  TEST      $<"
 	@ESPEAK_DATA_PATH=$(CURDIR) $< && echo "  PASSED    $<"
@@ -265,6 +271,7 @@ check:	tests/encoding.check \
 	tests/ssml.check \
 	tests/ssml-fuzzer.check \
 	tests/api.check \
+	tests/ieee80.check \
 	tests/dictionary.check \
 	tests/language-phonemes.check \
 	tests/language-replace.check \
diff --git a/tests/ieee80.c b/tests/ieee80.c
new file mode 100644
index 00000000..92aef073
--- /dev/null
+++ b/tests/ieee80.c
@@ -0,0 +1,64 @@
+/*
+ * Copyright (C) 2022 Ulrich Müller <ulm@gentoo.org>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see: <http://www.gnu.org/licenses/>.
+ *
+ *
+ * Alternatively, at your option, you can distribute this file under
+ * the terms of the 2-clause BSD license.
+ */
+
+#include "config.h"
+#include <assert.h>
+#include <math.h>
+#include <stdlib.h>
+#include "ieee80.h"
+
+int
+main(int argc, char **argv)
+{
+	(void)argc; (void)argv;	/* unused */
+
+	/* Define only constants that can be exactly represented both in
+	   decimal and in binary, in order to avoid rounding errors */
+	unsigned char in[][10] = {
+		{ 0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* 0 */
+		{ 0x3f,0xff,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* 1 */
+		{ 0xbf,0xff,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* -1 */
+		{ 0x40,0x00,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* 2 */
+		{ 0x3f,0xfe,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* 0.5 */
+		{ 0x3f,0xf7,0xc0,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* 0.005859375 */
+		{ 0x40,0x22,0x98,0x76,0x54,0x32,0x10,0x00,0x00,0x00 }, /* 40926266145 */
+		{ 0x7f,0xff,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* inf */
+		{ 0xff,0xff,0x80,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }, /* -inf */
+		{ 0x7f,0xff,0xc0,0x00,0x00,0x00,0x00,0x00,0x00,0x00 }  /* nan */
+	};
+
+	assert(ieee_extended_to_double(in[0]) == 0.);
+	assert(ieee_extended_to_double(in[1]) == 1.);
+	assert(ieee_extended_to_double(in[2]) == -1.);
+	assert(ieee_extended_to_double(in[3]) == 2.);
+	assert(ieee_extended_to_double(in[4]) == 0.5);
+	assert(ieee_extended_to_double(in[5]) == 0.005859375);
+	assert(ieee_extended_to_double(in[6]) == 40926266145.);
+#ifdef INFINITY
+	assert(ieee_extended_to_double(in[7]) == INFINITY);
+	assert(ieee_extended_to_double(in[8]) == -INFINITY);
+#endif
+#ifdef NAN
+	assert(isnan(ieee_extended_to_double(in[9])));
+#endif
+
+	return EXIT_SUCCESS;
+}