diff --git a/js/src/frontend/BytecodeEmitter.cpp b/js/src/frontend/BytecodeEmitter.cpp
index 35a4d74755c..2daf9afccff 100644
--- a/js/src/frontend/BytecodeEmitter.cpp
+++ b/js/src/frontend/BytecodeEmitter.cpp
@@ -6148,7 +6148,7 @@ BytecodeEmitter::emitCallOrNew(ParseNode* pn)
             return false;
     }
     if (pn->pn_xflags & PNX_SETCALL) {
-        if (!emit1(JSOP_SETCALL))
+        if (!emitUint16Operand(JSOP_THROWMSG, JSMSG_BAD_LEFTSIDE_OF_ASS))
             return false;
     }
     return true;
diff --git a/js/src/jit/BaselineCompiler.cpp b/js/src/jit/BaselineCompiler.cpp
index 9d7d59362cc..13baa43c20c 100644
--- a/js/src/jit/BaselineCompiler.cpp
+++ b/js/src/jit/BaselineCompiler.cpp
@@ -2901,14 +2901,15 @@ BaselineCompiler::emit_JSOP_TYPEOFEXPR()
     return emit_JSOP_TYPEOF();
 }
 
-typedef bool (*SetCallFn)(JSContext*);
-static const VMFunction SetCallInfo = FunctionInfo<SetCallFn>(js::SetCallOperation);
+typedef bool (*ThrowMsgFn)(JSContext*, const unsigned);
+static const VMFunction ThrowMsgInfo = FunctionInfo<ThrowMsgFn>(js::ThrowMsgOperation);
 
 bool
-BaselineCompiler::emit_JSOP_SETCALL()
+BaselineCompiler::emit_JSOP_THROWMSG()
 {
     prepareVMCall();
-    return callVM(SetCallInfo);
+    pushArg(Imm32(GET_UINT16(pc)));
+    return callVM(ThrowMsgInfo);
 }
 
 typedef bool (*ThrowFn)(JSContext*, HandleValue);
diff --git a/js/src/jit/BaselineCompiler.h b/js/src/jit/BaselineCompiler.h
index 0cbf37ef204..ddc9646d428 100644
--- a/js/src/jit/BaselineCompiler.h
+++ b/js/src/jit/BaselineCompiler.h
@@ -163,7 +163,7 @@ namespace jit {
     _(JSOP_INSTANCEOF)         \
     _(JSOP_TYPEOF)             \
     _(JSOP_TYPEOFEXPR)         \
-    _(JSOP_SETCALL)            \
+    _(JSOP_THROWMSG)           \
     _(JSOP_THROW)              \
     _(JSOP_THROWING)           \
     _(JSOP_TRY)                \
diff --git a/js/src/vm/Interpreter.cpp b/js/src/vm/Interpreter.cpp
index 13b31416feb..e48dfb37b1f 100644
--- a/js/src/vm/Interpreter.cpp
+++ b/js/src/vm/Interpreter.cpp
@@ -2923,12 +2923,12 @@ CASE(JSOP_FUNCALL)
     ADVANCE_AND_DISPATCH(0);
 }
 
-CASE(JSOP_SETCALL)
+CASE(JSOP_THROWMSG)
 {
-    JS_ALWAYS_FALSE(SetCallOperation(cx));
+    JS_ALWAYS_FALSE(ThrowMsgOperation(cx, GET_UINT16(REGS.pc)));
     goto error;
 }
-END_CASE(JSOP_SETCALL)
+END_CASE(JSOP_THROWMSG)
 
 CASE(JSOP_IMPLICITTHIS)
 CASE(JSOP_GIMPLICITTHIS)
@@ -4133,9 +4133,9 @@ js::DefFunOperation(JSContext* cx, HandleScript script, HandleObject scopeChain,
 }
 
 bool
-js::SetCallOperation(JSContext* cx)
+js::ThrowMsgOperation(JSContext* cx, const unsigned errorNum)
 {
-    JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, JSMSG_BAD_LEFTSIDE_OF_ASS);
+    JS_ReportErrorNumber(cx, GetErrorMessage, nullptr, errorNum);
     return false;
 }
 
diff --git a/js/src/vm/Interpreter.h b/js/src/vm/Interpreter.h
index a436e043d02..b5e54b19a62 100644
--- a/js/src/vm/Interpreter.h
+++ b/js/src/vm/Interpreter.h
@@ -399,7 +399,7 @@ bool
 DefFunOperation(JSContext* cx, HandleScript script, HandleObject scopeChain, HandleFunction funArg);
 
 bool
-SetCallOperation(JSContext* cx);
+ThrowMsgOperation(JSContext* cx, const unsigned errorNum);
 
 bool
 GetAndClearException(JSContext* cx, MutableHandleValue res);
diff --git a/js/src/vm/Opcodes.h b/js/src/vm/Opcodes.h
index 54f87f0bc4e..ab078b940d7 100644
--- a/js/src/vm/Opcodes.h
+++ b/js/src/vm/Opcodes.h
@@ -677,15 +677,16 @@
     macro(JSOP_STRICTNE,  73, "strictne",   "!==",        1,  2,  1, JOF_BYTE|JOF_DETECTING|JOF_LEFTASSOC|JOF_ARITH) \
     \
     /*
-     * Sometimes web pages do 'o.Item(i) = j'. This is not an early SyntaxError,
-     * for web compatibility. Instead we emit JSOP_SETCALL after the function
-     * call, an opcode that always throws.
+     * Sometimes we know when emitting that an operation will always throw.
+     *
+     * Throws the indicated JSMSG.
+     *
      *   Category: Statements
-     *   Type: Function
-     *   Operands:
+     *   Type: Exceptions
+     *   Operands: uint16_t msgNumber
      *   Stack: =>
      */ \
-    macro(JSOP_SETCALL,   74, "setcall",    NULL,         1,  0,  0, JOF_BYTE) \
+    macro(JSOP_THROWMSG,   74, "throwmsg",    NULL,         3,  0,  0, JOF_UINT16) \
     \
     /*
      * Sets up a for-in or for-each-in loop using the JSITER_* flag bits in
diff --git a/js/src/vm/Xdr.h b/js/src/vm/Xdr.h
index 964ed8d83a7..c8585dc3c80 100644
--- a/js/src/vm/Xdr.h
+++ b/js/src/vm/Xdr.h
@@ -29,7 +29,7 @@ namespace js {
  *
  *  https://developer.mozilla.org/en-US/docs/SpiderMonkey/Internals/Bytecode
  */
-static const uint32_t XDR_BYTECODE_VERSION_SUBTRAHEND = 272;
+static const uint32_t XDR_BYTECODE_VERSION_SUBTRAHEND = 273;
 static const uint32_t XDR_BYTECODE_VERSION =
     uint32_t(0xb973c0de - XDR_BYTECODE_VERSION_SUBTRAHEND);