diff --git a/NEWS b/NEWS
index 337fc0b44fd..7505ebcd39f 100644
--- a/NEWS
+++ b/NEWS
@@ -1,5 +1,11 @@
 PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
+?? ??? ????, PHP 8.4.2
+
+- Opcache:
+  . Fixed bug GH-16851 (JIT_G(enabled) not set correctly on other threads).
+    (dktapps)
+
 21 Nov 2024, PHP 8.4.1
 
 - BcMath:
diff --git a/ext/opcache/ZendAccelerator.c b/ext/opcache/ZendAccelerator.c
index e0f8cda2298..374fbcb1f94 100644
--- a/ext/opcache/ZendAccelerator.c
+++ b/ext/opcache/ZendAccelerator.c
@@ -3282,6 +3282,8 @@ static zend_result accel_post_startup(void)
 				zend_accel_error_noreturn(ACCEL_LOG_FATAL, "Could not enable JIT: could not use reserved buffer!");
 			} else {
 				zend_jit_startup(ZSMMG(reserved), jit_size, reattached);
+			} else {
+				zend_jit_startup_ok = true;
 			}
 		}
 #endif
diff --git a/ext/opcache/jit/zend_jit.c b/ext/opcache/jit/zend_jit.c
index 54ffd79a358..0c6ab6c5cbc 100644
--- a/ext/opcache/jit/zend_jit.c
+++ b/ext/opcache/jit/zend_jit.c
@@ -69,6 +69,8 @@ zend_jit_globals jit_globals;
 #define JIT_STUB_PREFIX "JIT$$"
 #define TRACE_PREFIX    "TRACE-"
 
+bool zend_jit_startup_ok = false;
+
 zend_ulong zend_jit_profile_counter = 0;
 int zend_jit_profile_counter_rid = -1;
 
@@ -3634,6 +3636,13 @@ static void zend_jit_reset_counters(void)
 
 void zend_jit_activate(void)
 {
+#ifdef ZTS
+	if (!zend_jit_startup_ok) {
+		JIT_G(enabled) = 0;
+		JIT_G(on) = 0;
+		return;
+	}
+#endif
 	zend_jit_profile_counter = 0;
 	if (JIT_G(on)) {
 		if (JIT_G(trigger) == ZEND_JIT_ON_HOT_COUNTERS) {
diff --git a/ext/opcache/jit/zend_jit.h b/ext/opcache/jit/zend_jit.h
index 0ce6c1a4409..9178d340a0e 100644
--- a/ext/opcache/jit/zend_jit.h
+++ b/ext/opcache/jit/zend_jit.h
@@ -100,6 +100,8 @@ typedef struct _zend_jit_trace_rec zend_jit_trace_rec;
 typedef struct _zend_jit_trace_stack_frame zend_jit_trace_stack_frame;
 typedef struct _sym_node zend_sym_node;
 
+extern bool zend_jit_startup_ok;
+
 typedef struct _zend_jit_globals {
 	bool enabled;
 	bool on;