diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 2338064df7..8c6a48d195 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -93,6 +93,7 @@
 			<&gpio_b 9 0xc 3 2 1>;
 		int-value = <1234>;
 		uint-value = <(-1234)>;
+		int64-value = /bits/ 64 <0x1111222233334444>;
 		interrupts-extended = <&irq 3 0>;
 	};
 
diff --git a/include/test/ut.h b/include/test/ut.h
index 04df8ba3af..ab861588a8 100644
--- a/include/test/ut.h
+++ b/include/test/ut.h
@@ -104,6 +104,22 @@ int ut_check_console_dump(struct unit_test_state *uts, int total_bytes);
 	}								\
 }
 
+/* Assert that two 64 int expressions are equal */
+#define ut_asserteq_64(expr1, expr2) {					\
+	u64 _val1 = (expr1), _val2 = (expr2);				\
+									\
+	if (_val1 != _val2) {						\
+		ut_failf(uts, __FILE__, __LINE__, __func__,		\
+			 #expr1 " == " #expr2,				\
+			 "Expected %#llx (%lld), got %#llx (%lld)",	\
+			 (unsigned long long)_val1,			\
+			 (unsigned long long)_val1,			\
+			 (unsigned long long)_val2,			\
+			 (unsigned long long)_val2);			\
+		return CMD_RET_FAILURE;					\
+	}								\
+}
+
 /* Assert that two string expressions are equal */
 #define ut_asserteq_str(expr1, expr2) {					\
 	const char *_val1 = (expr1), *_val2 = (expr2);			\
diff --git a/test/dm/test-fdt.c b/test/dm/test-fdt.c
index 3500ab1b46..b39777f082 100644
--- a/test/dm/test-fdt.c
+++ b/test/dm/test-fdt.c
@@ -867,6 +867,7 @@ static int dm_test_read_int(struct unit_test_state *uts)
 	u32 val32;
 	s32 sval;
 	uint val;
+	u64 val64;
 
 	ut_assertok(uclass_first_device_err(UCLASS_TEST_FDT, &dev));
 	ut_asserteq_str("a-test", dev->name);
@@ -891,6 +892,15 @@ static int dm_test_read_int(struct unit_test_state *uts)
 	ut_assertok(dev_read_u32u(dev, "uint-value", &val));
 	ut_asserteq(-1234, val);
 
+	ut_assertok(dev_read_u64(dev, "int64-value", &val64));
+	ut_asserteq_64(0x1111222233334444, val64);
+
+	ut_asserteq_64(-EINVAL, dev_read_u64(dev, "missing", &val64));
+	ut_asserteq_64(6, dev_read_u64_default(dev, "missing", 6));
+
+	ut_asserteq_64(0x1111222233334444,
+		       dev_read_u64_default(dev, "int64-value", 6));
+
 	return 0;
 }
 DM_TEST(dm_test_read_int, DM_TESTF_SCAN_PDATA | DM_TESTF_SCAN_FDT);