diff --git a/M2/Macaulay2/d/binding.d b/M2/Macaulay2/d/binding.d
index 4b8d5aaa04f..97c60b07dff 100644
--- a/M2/Macaulay2/d/binding.d
+++ b/M2/Macaulay2/d/binding.d
@@ -318,6 +318,7 @@ bumpPrecedence();
      export breakpointS    := special("breakpoint",    unaryop, precSpace, wide);
      export profileS       := special("profile",       unaryop, precSpace, wide);
      export shieldS        := special("shield",        unaryop, precSpace, wide);
+     export threadLockS    := special("threadLock",    unaryop, precSpace, wide);
      export throwS         := special("throw",        nunaryop, precSpace, wide);
      export returnS        := special("return",       nunaryop, precSpace, wide);
      export breakS         := special("break",        nunaryop, precSpace, wide);
diff --git a/M2/Macaulay2/d/pthread.d b/M2/Macaulay2/d/pthread.d
index acd635f8e95..88069e7fb9c 100644
--- a/M2/Macaulay2/d/pthread.d
+++ b/M2/Macaulay2/d/pthread.d
@@ -3,6 +3,7 @@ use evaluate;
 use expr;
 
 header "#include \"../system/supervisorinterface.h\"";
+header "#include <errno.h>"; -- for EBUSY
 
 
 taskCreatePush(f:function(TaskCellBody):null,tb:TaskCellBody) ::=  Ccode(taskPointer,
@@ -231,6 +232,20 @@ export getIOThreadMode(e:Expr):Expr := (
     else WrongArg("a file or ()"));
 setupfun("getIOThreadMode", getIOThreadMode);
 
+-- TODO: what if we cancel a task before it unlocks the mutex?
+mutex := newMutex;
+threadLock(c:Code):Expr := (
+    r := 0;
+    while (r = trylock(mutex); r == Ccode(int, "EBUSY")) do (
+	f := eval(dummyCode); -- handle interrupts
+	when f is Error do return f else nothing);
+    if r == 0 then (
+	e := eval(c);
+	unlock(mutex);
+	e)
+    else buildErrorPacketErrno("threadLock", r));
+setupop(threadLockS, threadLock);
+
 -- Local Variables:
 -- compile-command: "echo \"make: Entering directory \\`$M2BUILDDIR/Macaulay2/d'\" && make -C $M2BUILDDIR/Macaulay2/d pthread.o "
 -- End:
diff --git a/M2/Macaulay2/d/pthread0.d b/M2/Macaulay2/d/pthread0.d
index d6d2d6607cc..1210ffb168f 100644
--- a/M2/Macaulay2/d/pthread0.d
+++ b/M2/Macaulay2/d/pthread0.d
@@ -30,6 +30,7 @@ export SpinLock := atomicType "struct spinlockStructure";
 export init(x:ThreadMutex) ::= Ccode(int, "pthread_mutex_init(&(",lvalue(x),"),NULL)");
 export destroy(x:ThreadMutex) ::= Ccode(int, "pthread_mutex_destroy(&(",lvalue(x),"))");
 export lock(x:ThreadMutex) ::= Ccode(int, "pthread_mutex_lock(&(",lvalue(x),"))");
+export trylock(x:ThreadMutex) ::= Ccode(int, "pthread_mutex_trylock(&(",lvalue(x),"))");
 export unlock(x:ThreadMutex) ::= Ccode(int, "pthread_mutex_unlock(&(",lvalue(x),"))");
 export getthreadself() ::= Ccode(Thread, "pthread_self()");
 
diff --git a/M2/Macaulay2/m2/exports.m2 b/M2/Macaulay2/m2/exports.m2
index 72f7184cc7f..4b551637a70 100644
--- a/M2/Macaulay2/m2/exports.m2
+++ b/M2/Macaulay2/m2/exports.m2
@@ -1203,6 +1203,7 @@ export {
 	"texMath",
 	"then",
 	"threadLocal",
+	"threadLock",
 	"throw",
 	"time",
 	"times",
diff --git a/M2/Macaulay2/tests/normal/threads.m2 b/M2/Macaulay2/tests/normal/threads.m2
index 312a42b3431..8a4943d6286 100644
--- a/M2/Macaulay2/tests/normal/threads.m2
+++ b/M2/Macaulay2/tests/normal/threads.m2
@@ -85,6 +85,13 @@ assert Equation(getIOThreadMode f, 2)
 
 removeFile fn
 
+-- threadLock
+-- mutable lists are *not* thread safe
+-- if they ever become thread safe, then change this test
+x = new MutableList
+taskResult \ apply(1000, i -> schedule(() -> threadLock x##x = null));
+assert Equation(#x, 1000)
+
 -- Local Variables:
 -- compile-command: "make -C $M2BUILDDIR/Macaulay2/packages/Macaulay2Doc/test threads.out"
 -- End: