diff --git a/src/V3LinkJump.cpp b/src/V3LinkJump.cpp
index 566060394..3b02c867a 100644
--- a/src/V3LinkJump.cpp
+++ b/src/V3LinkJump.cpp
@@ -52,6 +52,7 @@ private:
     AstNodeFTask* m_ftaskp;  // Current function/task
     AstWhile* m_loopp;  // Current loop
     bool m_loopInc;  // In loop increment
+    bool m_inFork;  // Under fork
     int m_modRepeatNum;  // Repeat counter
     BlockStack m_blockStack;  // All begin blocks above current node
 
@@ -136,9 +137,14 @@ private:
     }
     virtual void visit(AstNodeBlock* nodep) VL_OVERRIDE {
         UINFO(8, "  " << nodep << endl);
+        bool oldFork = m_inFork;
         m_blockStack.push_back(nodep);
-        iterateChildren(nodep);
+        {
+            m_inFork = m_inFork || VN_IS(nodep, Fork);
+            iterateChildren(nodep);
+        }
         m_blockStack.pop_back();
+        m_inFork = oldFork;
     }
     virtual void visit(AstRepeat* nodep) VL_OVERRIDE {
         // So later optimizations don't need to deal with them,
@@ -185,7 +191,11 @@ private:
     virtual void visit(AstReturn* nodep) VL_OVERRIDE {
         iterateChildren(nodep);
         AstFunc* funcp = VN_CAST(m_ftaskp, Func);
-        if (!m_ftaskp) {
+        if (m_inFork) {
+            nodep->v3error("Return isn't legal under fork (IEEE 1800-2017 9.2.3)");
+            VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+            return;
+        } else if (!m_ftaskp) {
             nodep->v3error("Return isn't underneath a task or function");
         } else if (funcp && !nodep->lhsp()) {
             nodep->v3error("Return underneath a function should have return value");
@@ -268,6 +278,7 @@ public:
     explicit LinkJumpVisitor(AstNetlist* nodep) {
         m_modp = NULL;
         m_ftaskp = NULL;
+        m_inFork = false;
         m_loopp = NULL;
         m_loopInc = false;
         m_modRepeatNum = 0;
diff --git a/src/V3LinkParse.cpp b/src/V3LinkParse.cpp
index 51051876e..ed78d7546 100644
--- a/src/V3LinkParse.cpp
+++ b/src/V3LinkParse.cpp
@@ -490,17 +490,6 @@ private:
         }
         iterateChildren(nodep);
     }
-    virtual void visit(AstFork* nodep) VL_OVERRIDE {
-        if (v3Global.opt.bboxUnsup()) {
-            AstBegin* newp
-                = new AstBegin(nodep->fileline(), nodep->name(), nodep->stmtsp()->unlinkFrBack());
-            nodep->replaceWith(newp);
-            VL_DO_DANGLING(nodep->deleteTree(), nodep);
-        } else {
-            nodep->v3error("Unsupported: fork statements");
-            // TBD might support only normal join, if so complain about other join flavors
-        }
-    }
     virtual void visit(AstCase* nodep) VL_OVERRIDE {
         V3Config::applyCase(nodep);
         cleanFileline(nodep);
diff --git a/src/V3Width.cpp b/src/V3Width.cpp
index 699020441..b57fe02c7 100644
--- a/src/V3Width.cpp
+++ b/src/V3Width.cpp
@@ -552,6 +552,23 @@ private:
         nodep->v3warn(STMTDLY, "Unsupported: Ignoring delay on this delayed statement.");
         VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
     }
+    virtual void visit(AstFork* nodep) VL_OVERRIDE {
+        if (VN_IS(m_ftaskp, Func) && !nodep->joinType().joinNone()) {
+            nodep->v3error("Only fork .. join_none is legal in functions. "
+                           "(IEEE 1800-2017 13.4.4)");
+            VL_DO_DANGLING(pushDeletep(nodep->unlinkFrBack()), nodep);
+            return;
+        }
+        if (v3Global.opt.bboxUnsup()) {
+            AstBegin* newp
+                = new AstBegin(nodep->fileline(), nodep->name(), nodep->stmtsp()->unlinkFrBack());
+            nodep->replaceWith(newp);
+            VL_DO_DANGLING(nodep->deleteTree(), nodep);
+        } else {
+            nodep->v3error("Unsupported: fork statements");
+            // TBD might support only normal join, if so complain about other join flavors
+        }
+    }
     virtual void visit(AstToLowerN* nodep) VL_OVERRIDE {
         if (m_vup->prelim()) {
             iterateCheckString(nodep, "LHS", nodep->lhsp(), BOTH);
diff --git a/test_regress/t/t_fork.out b/test_regress/t/t_fork.out
index 1f9b98a83..5d76dd536 100644
--- a/test_regress/t/t_fork.out
+++ b/test_regress/t/t_fork.out
@@ -1,4 +1,5 @@
 %Error: t/t_fork.v:10:14: Unsupported: fork statements
+                        : ... In instance t
    10 |       fork : fblk
       |              ^~~~
 %Error: Exiting due to
diff --git a/test_regress/t/t_fork_func2_bad.out b/test_regress/t/t_fork_func2_bad.out
new file mode 100644
index 000000000..16cdd6242
--- /dev/null
+++ b/test_regress/t/t_fork_func2_bad.out
@@ -0,0 +1,5 @@
+%Error: t/t_fork_func2_bad.v:10:7: Only fork .. join_none is legal in functions. (IEEE 1800-2017 13.4.4)
+                                 : ... In instance t
+   10 |       fork
+      |       ^~~~
+%Error: Exiting due to
diff --git a/test_regress/t/t_fork_func2_bad.pl b/test_regress/t/t_fork_func2_bad.pl
new file mode 100755
index 000000000..2f077ff56
--- /dev/null
+++ b/test_regress/t/t_fork_func2_bad.pl
@@ -0,0 +1,20 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2019 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(linter => 1);
+
+compile(
+    verilator_flags2 => ['--lint-only'],
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_fork_func2_bad.v b/test_regress/t/t_fork_func2_bad.v
new file mode 100644
index 000000000..c777a5c58
--- /dev/null
+++ b/test_regress/t/t_fork_func2_bad.v
@@ -0,0 +1,21 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2020 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t(/*AUTOARG*/);
+
+   function int f;
+      fork
+         ;
+      join_any  // Illegal 13.4.4
+   endfunction
+
+   int i;
+
+   initial begin
+      i = f();
+   end
+
+endmodule
diff --git a/test_regress/t/t_fork_func_bad.out b/test_regress/t/t_fork_func_bad.out
new file mode 100644
index 000000000..0fdf968a9
--- /dev/null
+++ b/test_regress/t/t_fork_func_bad.out
@@ -0,0 +1,4 @@
+%Error: t/t_fork_func_bad.v:11:10: Return isn't legal under fork (IEEE 1800-2017 9.2.3)
+   11 |          return 0;   
+      |          ^~~~~~
+%Error: Exiting due to
diff --git a/test_regress/t/t_fork_func_bad.pl b/test_regress/t/t_fork_func_bad.pl
new file mode 100755
index 000000000..2f077ff56
--- /dev/null
+++ b/test_regress/t/t_fork_func_bad.pl
@@ -0,0 +1,20 @@
+#!/usr/bin/env perl
+if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); die; }
+# DESCRIPTION: Verilator: Verilog Test driver/expect definition
+#
+# Copyright 2019 by Wilson Snyder. This program is free software; you
+# can redistribute it and/or modify it under the terms of either the GNU
+# Lesser General Public License Version 3 or the Perl Artistic License
+# Version 2.0.
+# SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+
+scenarios(linter => 1);
+
+compile(
+    verilator_flags2 => ['--lint-only'],
+    fails => 1,
+    expect_filename => $Self->{golden_filename},
+    );
+
+ok(1);
+1;
diff --git a/test_regress/t/t_fork_func_bad.v b/test_regress/t/t_fork_func_bad.v
new file mode 100644
index 000000000..c4a67a6f1
--- /dev/null
+++ b/test_regress/t/t_fork_func_bad.v
@@ -0,0 +1,21 @@
+// DESCRIPTION: Verilator: Verilog Test module
+//
+// This file ONLY is placed under the Creative Commons Public Domain, for
+// any use, without warranty, 2020 by Wilson Snyder.
+// SPDX-License-Identifier: CC0-1.0
+
+module t(/*AUTOARG*/);
+
+   function int f;
+      fork
+         return 0;  // Illegal 9.3.2
+      join_none
+   endfunction
+
+   int i;
+
+   initial begin
+      i = f();
+   end
+
+endmodule