diff --git a/src/V3LinkDot.cpp b/src/V3LinkDot.cpp
index 07914fab5..6079f3b3d 100644
--- a/src/V3LinkDot.cpp
+++ b/src/V3LinkDot.cpp
@@ -2529,7 +2529,13 @@ class LinkDotIfaceVisitor final : public VNVisitor {
     void visit(AstModportVarRef* nodep) override {  // IfaceVisitor::
         UINFO(5, "   fiv: " << nodep);
         iterateChildren(nodep);
-        VSymEnt* const symp = m_curSymp->findIdFallback(nodep->name());
+        VSymEnt* symp = nullptr;
+        if (nodep->m_exp()) {
+            nodep->v3warn(E_UNSUPPORTED,
+                          "Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)");
+        } else {
+            symp = m_curSymp->findIdFallback(nodep->name());
+        }
         if (!symp) {
             nodep->v3error("Modport item not found: " << nodep->prettyNameQ());
         } else if (AstVar* const varp = VN_CAST(symp->nodep(), Var)) {
diff --git a/test_regress/t/t_interface_modport_expr.out b/test_regress/t/t_interface_modport_expr.out
new file mode 100644
index 000000000..277926b00
--- /dev/null
+++ b/test_regress/t/t_interface_modport_expr.out
@@ -0,0 +1,39 @@
+%Error-UNSUPPORTED: t/t_interface_modport_expr.v:15:22: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   15 |   modport mp1(input .a(sig_a), output .b(sig_b));
+      |                      ^
+                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
+%Error: t/t_interface_modport_expr.v:15:22: Modport item not found: 'a'
+   15 |   modport mp1(input .a(sig_a), output .b(sig_b));
+      |                      ^
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error-UNSUPPORTED: t/t_interface_modport_expr.v:15:40: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   15 |   modport mp1(input .a(sig_a), output .b(sig_b));
+      |                                        ^
+%Error: t/t_interface_modport_expr.v:15:40: Modport item not found: 'b'
+   15 |   modport mp1(input .a(sig_a), output .b(sig_b));
+      |                                        ^
+%Error-UNSUPPORTED: t/t_interface_modport_expr.v:16:22: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   16 |   modport mp2(input .a(sig_c), output .b(sig_d));
+      |                      ^
+%Error: t/t_interface_modport_expr.v:16:22: Modport item not found: 'a'
+   16 |   modport mp2(input .a(sig_c), output .b(sig_d));
+      |                      ^
+%Error-UNSUPPORTED: t/t_interface_modport_expr.v:16:40: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   16 |   modport mp2(input .a(sig_c), output .b(sig_d));
+      |                                        ^
+%Error: t/t_interface_modport_expr.v:16:40: Modport item not found: 'b'
+   16 |   modport mp2(input .a(sig_c), output .b(sig_d));
+      |                                        ^
+%Error: t/t_interface_modport_expr.v:28:18: Can't find definition of 'a' in dotted variable/method: 'i.a'
+   28 |   assign i.b = i.a;
+      |                  ^
+%Error: t/t_interface_modport_expr.v:28:12: Can't find definition of 'b' in dotted variable/method: 'i.b'
+   28 |   assign i.b = i.a;
+      |            ^
+%Error: t/t_interface_modport_expr.v:22:18: Can't find definition of 'a' in dotted variable/method: 'i.a'
+   22 |   assign i.b = i.a;
+      |                  ^
+%Error: t/t_interface_modport_expr.v:22:12: Can't find definition of 'b' in dotted variable/method: 'i.b'
+   22 |   assign i.b = i.a;
+      |            ^
+%Error: Exiting due to
diff --git a/test_regress/t/t_interface_modport_expr.py b/test_regress/t/t_interface_modport_expr.py
index c6e56559a..3fada1a58 100755
--- a/test_regress/t/t_interface_modport_expr.py
+++ b/test_regress/t/t_interface_modport_expr.py
@@ -11,8 +11,10 @@ import vltest_bootstrap
 
 test.scenarios('simulator')
 
-test.compile(verilator_flags2=["--binary"])
+test.compile(fails=test.vlt_all, expect_filename=test.golden_filename,
+             verilator_flags2=["--binary"])
 
-test.execute()
+if not test.vlt_all:
+    test.execute()
 
 test.passes()
diff --git a/test_regress/t/t_interface_modport_expr_partsel.out b/test_regress/t/t_interface_modport_expr_partsel.out
new file mode 100644
index 000000000..deb4ee46c
--- /dev/null
+++ b/test_regress/t/t_interface_modport_expr_partsel.out
@@ -0,0 +1,39 @@
+%Error-UNSUPPORTED: t/t_interface_modport_expr_partsel.v:16:22: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   16 |   modport mp1(input .in(a[7:0]), output .out(b));
+      |                      ^~
+                    ... For error description see https://verilator.org/warn/UNSUPPORTED?v=latest
+%Error: t/t_interface_modport_expr_partsel.v:16:22: Modport item not found: 'in'
+   16 |   modport mp1(input .in(a[7:0]), output .out(b));
+      |                      ^~
+        ... See the manual at https://verilator.org/verilator_doc.html?v=latest for more assistance.
+%Error-UNSUPPORTED: t/t_interface_modport_expr_partsel.v:16:42: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   16 |   modport mp1(input .in(a[7:0]), output .out(b));
+      |                                          ^~~
+%Error: t/t_interface_modport_expr_partsel.v:16:42: Modport item not found: 'out'
+   16 |   modport mp1(input .in(a[7:0]), output .out(b));
+      |                                          ^~~
+%Error-UNSUPPORTED: t/t_interface_modport_expr_partsel.v:17:22: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   17 |   modport mp2(input .in(a[15:8]), output .out(c));
+      |                      ^~
+%Error: t/t_interface_modport_expr_partsel.v:17:22: Modport item not found: 'in'
+   17 |   modport mp2(input .in(a[15:8]), output .out(c));
+      |                      ^~
+%Error-UNSUPPORTED: t/t_interface_modport_expr_partsel.v:17:43: Unsupported: Modport expressions (IEEE 1800-2023 25.5.4)
+   17 |   modport mp2(input .in(a[15:8]), output .out(c));
+      |                                           ^~~
+%Error: t/t_interface_modport_expr_partsel.v:17:43: Modport item not found: 'out'
+   17 |   modport mp2(input .in(a[15:8]), output .out(c));
+      |                                           ^~~
+%Error: t/t_interface_modport_expr_partsel.v:29:21: Can't find definition of 'in' in dotted variable/method: 'i.in'
+   29 |   assign i.out = ~i.in;
+      |                     ^~
+%Error: t/t_interface_modport_expr_partsel.v:29:12: Can't find definition of 'out' in dotted variable/method: 'i.out'
+   29 |   assign i.out = ~i.in;
+      |            ^~~
+%Error: t/t_interface_modport_expr_partsel.v:23:20: Can't find definition of 'in' in dotted variable/method: 'i.in'
+   23 |   assign i.out = i.in;
+      |                    ^~
+%Error: t/t_interface_modport_expr_partsel.v:23:12: Can't find definition of 'out' in dotted variable/method: 'i.out'
+   23 |   assign i.out = i.in;
+      |            ^~~
+%Error: Exiting due to
diff --git a/test_regress/t/t_interface_modport_expr_partsel.py b/test_regress/t/t_interface_modport_expr_partsel.py
index c6e56559a..3fada1a58 100755
--- a/test_regress/t/t_interface_modport_expr_partsel.py
+++ b/test_regress/t/t_interface_modport_expr_partsel.py
@@ -11,8 +11,10 @@ import vltest_bootstrap
 
 test.scenarios('simulator')
 
-test.compile(verilator_flags2=["--binary"])
+test.compile(fails=test.vlt_all, expect_filename=test.golden_filename,
+             verilator_flags2=["--binary"])
 
-test.execute()
+if not test.vlt_all:
+    test.execute()
 
 test.passes()