diff --git a/ivtest/ivltests/udp_ansi_initial_nonreg_fail.v b/ivtest/ivltests/udp_ansi_initial_nonreg_fail.v
new file mode 100644
index 000000000..25ce9da6d
--- /dev/null
+++ b/ivtest/ivltests/udp_ansi_initial_nonreg_fail.v
@@ -0,0 +1,8 @@
+// Check that an ANSI-style UDP output initializer requires a reg output.
+
+primitive udp_ansi_initial_nonreg_fail (output o = 1'b0, input i);
+  table
+    0 : 0;
+    1 : 1;
+  endtable
+endprimitive
diff --git a/ivtest/ivltests/udp_ansi_initial_reg.v b/ivtest/ivltests/udp_ansi_initial_reg.v
new file mode 100644
index 000000000..cfbcdd6b1
--- /dev/null
+++ b/ivtest/ivltests/udp_ansi_initial_reg.v
@@ -0,0 +1,21 @@
+// Check that an ANSI-style UDP reg output can have an initializer.
+
+primitive udp_ansi_initial_reg (output reg o = 1'b0, input i);
+  table
+    0 : ? : 0;
+    1 : ? : 1;
+  endtable
+endprimitive
+
+module test;
+  reg i;
+  wire o;
+
+  udp_ansi_initial_reg i_udp(o, i);
+
+  initial begin
+    i = 1'b0;
+    #1;
+    $display("PASSED");
+  end
+endmodule
diff --git a/ivtest/ivltests/udp_initial_nonreg_fail.v b/ivtest/ivltests/udp_initial_nonreg_fail.v
new file mode 100644
index 000000000..689b63e45
--- /dev/null
+++ b/ivtest/ivltests/udp_initial_nonreg_fail.v
@@ -0,0 +1,12 @@
+// Check that an old-style UDP initial statement requires a reg output.
+
+primitive udp_initial_nonreg_fail (o, i);
+  output o;
+  input i;
+  initial o = 1'b0;
+
+  table
+    0 : 0;
+    1 : 1;
+  endtable
+endprimitive
diff --git a/ivtest/ivltests/udp_port_decl_conflict_fail.v b/ivtest/ivltests/udp_port_decl_conflict_fail.v
new file mode 100644
index 000000000..00ebdfe55
--- /dev/null
+++ b/ivtest/ivltests/udp_port_decl_conflict_fail.v
@@ -0,0 +1,12 @@
+// Check that conflicting UDP port declarations generate an error.
+
+primitive udp_port_decl_conflict_fail (o, i);
+  output o;
+  input o;
+  input i;
+
+  table
+    0 : 0;
+    1 : 1;
+  endtable
+endprimitive
diff --git a/ivtest/regress-vvp.list b/ivtest/regress-vvp.list
index e81949a7b..85cfa1dda 100644
--- a/ivtest/regress-vvp.list
+++ b/ivtest/regress-vvp.list
@@ -430,7 +430,11 @@ test_va_math			vvp_tests/test_va_math.json
 test_vams_math			vvp_tests/test_vams_math.json
 timing_check_syntax		vvp_tests/timing_check_syntax.json
 timing_check_delayed_signals	vvp_tests/timing_check_delayed_signals.json
+udp_ansi_initial_nonreg_fail	vvp_tests/udp_ansi_initial_nonreg_fail.json
+udp_ansi_initial_reg		vvp_tests/udp_ansi_initial_reg.json
 udp_empty_table_fail		vvp_tests/udp_empty_table_fail.json
+udp_initial_nonreg_fail		vvp_tests/udp_initial_nonreg_fail.json
+udp_port_decl_conflict_fail	vvp_tests/udp_port_decl_conflict_fail.json
 uwire_fail2			vvp_tests/uwire_fail2.json
 uwire_fail3			vvp_tests/uwire_fail3.json
 value_range1			vvp_tests/value_range1.json
diff --git a/ivtest/vvp_tests/udp_ansi_initial_nonreg_fail.json b/ivtest/vvp_tests/udp_ansi_initial_nonreg_fail.json
new file mode 100644
index 000000000..1a984c32f
--- /dev/null
+++ b/ivtest/vvp_tests/udp_ansi_initial_nonreg_fail.json
@@ -0,0 +1,4 @@
+{
+    "type"   : "CE",
+    "source" : "udp_ansi_initial_nonreg_fail.v"
+}
diff --git a/ivtest/vvp_tests/udp_ansi_initial_reg.json b/ivtest/vvp_tests/udp_ansi_initial_reg.json
new file mode 100644
index 000000000..5f72fea49
--- /dev/null
+++ b/ivtest/vvp_tests/udp_ansi_initial_reg.json
@@ -0,0 +1,4 @@
+{
+    "type"   : "normal",
+    "source" : "udp_ansi_initial_reg.v"
+}
diff --git a/ivtest/vvp_tests/udp_initial_nonreg_fail.json b/ivtest/vvp_tests/udp_initial_nonreg_fail.json
new file mode 100644
index 000000000..735d978fd
--- /dev/null
+++ b/ivtest/vvp_tests/udp_initial_nonreg_fail.json
@@ -0,0 +1,4 @@
+{
+    "type"   : "CE",
+    "source" : "udp_initial_nonreg_fail.v"
+}
diff --git a/ivtest/vvp_tests/udp_port_decl_conflict_fail.json b/ivtest/vvp_tests/udp_port_decl_conflict_fail.json
new file mode 100644
index 000000000..56a5fdb42
--- /dev/null
+++ b/ivtest/vvp_tests/udp_port_decl_conflict_fail.json
@@ -0,0 +1,4 @@
+{
+    "type"   : "CE",
+    "source" : "udp_port_decl_conflict_fail.v"
+}