diff --git a/vvp/codes.h b/vvp/codes.h
index 35f2776a6..4a730bec0 100644
--- a/vvp/codes.h
+++ b/vvp/codes.h
@@ -90,6 +90,7 @@ extern bool of_DELAY(vthread_t thr, vvp_code_t code);
 extern bool of_DELAYX(vthread_t thr, vvp_code_t code);
 extern bool of_DELETE_OBJ(vthread_t thr, vvp_code_t code);
 extern bool of_DISABLE(vthread_t thr, vvp_code_t code);
+extern bool of_DISABLE_FORK(vthread_t thr, vvp_code_t code);
 extern bool of_DIV(vthread_t thr, vvp_code_t code);
 extern bool of_DIV_S(vthread_t thr, vvp_code_t code);
 extern bool of_DIV_WR(vthread_t thr, vvp_code_t code);
diff --git a/vvp/compile.cc b/vvp/compile.cc
index 56ef37aad..40a16300c 100644
--- a/vvp/compile.cc
+++ b/vvp/compile.cc
@@ -140,6 +140,7 @@ static const struct opcode_table_s opcode_table[] = {
       { "%delay",  of_DELAY,  2,  {OA_BIT1,     OA_BIT2,     OA_NONE} },
       { "%delayx", of_DELAYX, 1,  {OA_NUMBER,   OA_NONE,     OA_NONE} },
       { "%delete/obj",of_DELETE_OBJ,1,{OA_FUNC_PTR,OA_NONE,  OA_NONE} },
+      { "%disable/fork",of_DISABLE_FORK,0,{OA_NONE,OA_NONE,  OA_NONE} },
       { "%div",    of_DIV,    3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
       { "%div/s",  of_DIV_S,  3,  {OA_BIT1,     OA_BIT2,     OA_NUMBER} },
       { "%div/wr",   of_DIV_WR,  0, {OA_NONE,   OA_NONE,     OA_NONE} },
diff --git a/vvp/opcodes.txt b/vvp/opcodes.txt
index 69c72ab59..daaacba5d 100644
--- a/vvp/opcodes.txt
+++ b/vvp/opcodes.txt
@@ -280,7 +280,7 @@ number that the vector is compared with.
 Compare real values for equality and less-then. This opcode pops to
 values from the real-value stack and writes the comparison result to
 bits 4/5. The expressions (a < b) and (a==b) are calculated, with (b)
-poped from the stack first, then (a).
+popped from the stack first, then (a).
 
 * %cmp/ws <bit-l>, <bit-r>
 * %cmp/wu <bit-l>, <bit-r>
@@ -314,7 +314,7 @@ instruction removes two strings from the stack.
 * %concati/str <string>
 
 Pop the top string, and concatenate it to the new top string. Or think
-of it as possing the tail, then the head, concatenating them, and
+of it as passing the tail, then the head, concatenating them, and
 pushing the result. The stack starts with two strings in the stack,
 and ends with one string in the stack.
 
@@ -401,6 +401,11 @@ This instruction terminates threads that are part of a specific
 scope. The label identifies the scope in question, and the threads are
 the threads that are currently within that scope.
 
+* %disable/fork
+
+This instruction terminates all the detached children for the current
+thread. There should not be any non-detached children.
+
 
 * %div <bit-l>, <bit-r>, <wid>
 * %div/s <bit-l>, <bit-r>, <wid>
@@ -1038,9 +1043,9 @@ top of the object stack. The cobject is NOT popped.
 * %store/reala <var-label>, <index>
 
 This pops the top of the real variable stack and write it to the
-object variable given bu the label.
+object variable given by the label.
 
-The areal version is similar, but writes to a real array using the
+The reala version is similar, but writes to a real array using the
 index in the index register <index>
 
 * %store/str <var-label>
diff --git a/vvp/vthread.cc b/vvp/vthread.cc
index 38d133774..04896e7a4 100644
--- a/vvp/vthread.cc
+++ b/vvp/vthread.cc
@@ -2215,6 +2215,36 @@ bool of_DISABLE(vthread_t thr, vvp_code_t cp)
       return ! disabled_myself_flag;
 }
 
+/*
+ * Implement the %disable/fork (SystemVerilog) instruction by disabling
+ * all the detached children of the given thread.
+ */
+bool of_DISABLE_FORK(vthread_t thr, vvp_code_t)
+{
+	/* If a %disable/fork is being executed then the parent thread
+	 * cannot be waiting in a join. */
+      assert(thr->i_am_joining == 0);
+
+	/* There should be no active children to disable. */
+      assert(thr->children.empty());
+
+	/* Disable any detached children. */
+fprintf(stderr, "Sorry: %%disable/fork has not been implemented. It "
+                "will be ignored.\n");
+#if 0
+      while (!thr->children.empty()) {
+	    vthread_t tmp = *(thr->children.begin());
+	    assert(tmp);
+	    assert(tmp->parent == thr);
+	      /* Disabling the children can never match the parent thread. */
+	    assert(! do_disable(tmp, thr));
+	    vthread_reap(tmp);
+      }
+#endif
+
+      return true;
+}
+
 /*
  * This function divides a 2-word number {high, a} by a 1-word
  * number. Assume that high < b.