diff --git a/libuavcan/test/dsdl_test/dsdl_uavcan_compilability.cpp b/libuavcan/test/dsdl_test/dsdl_uavcan_compilability.cpp
index 8fc57ac7fb..5643ade02d 100644
--- a/libuavcan/test/dsdl_test/dsdl_uavcan_compilability.cpp
+++ b/libuavcan/test/dsdl_test/dsdl_uavcan_compilability.cpp
@@ -22,6 +22,7 @@
 
 #include <root_ns_a/Deep.hpp>
 #include <root_ns_a/UnionTest.hpp>
+#include <root_ns_a/UnionTest4.hpp>
 
 template <typename T>
 static bool validateYaml(const T& obj, const std::string& reference)
@@ -200,6 +201,38 @@ TEST(Dsdl, Union)
 }
 
 
+
+TEST(Dsdl, UnionTagWidth)
+{
+    using root_ns_a::UnionTest4;
+
+    ASSERT_EQ(2, UnionTest4::MinBitLen);
+    ASSERT_EQ(8, UnionTest4::MaxBitLen);
+
+    UnionTest4 s;
+
+    {
+        uavcan::StaticTransferBuffer<100> buf;
+        uavcan::BitStream bs_wr(buf);
+        uavcan::ScalarCodec sc_wr(bs_wr);
+
+        ASSERT_EQ(1, UnionTest4::encode(s, sc_wr));
+        ASSERT_EQ("00000000", bs_wr.toString());
+    }
+
+    {
+        uavcan::StaticTransferBuffer<100> buf;
+        uavcan::BitStream bs_wr(buf);
+        uavcan::ScalarCodec sc_wr(bs_wr);
+
+        s.to<UnionTest4::Tag::third>() = 1U << 5U;   // 32, 0b100000
+
+        ASSERT_EQ(1, UnionTest4::encode(s, sc_wr));
+        ASSERT_EQ("10100000", bs_wr.toString());
+    }
+}
+
+
 TEST(Dsdl, ParamGetSetRequestUnion)
 {
     uavcan::protocol::param::GetSet::Request req;
diff --git a/libuavcan/test/dsdl_test/root_ns_a/UnionTest4.uavcan b/libuavcan/test/dsdl_test/root_ns_a/UnionTest4.uavcan
new file mode 100644
index 0000000000..05bfb5c98c
--- /dev/null
+++ b/libuavcan/test/dsdl_test/root_ns_a/UnionTest4.uavcan
@@ -0,0 +1,6 @@
+# A union of four items; tag 2 bits wide, total length 1 byte
+@union          # 2 bits
+Empty first     # Tag value 0
+uint5 second    # Tag value 1
+uint6 third     # Tag value 2
+int2  fourth    # Tag value 3