diff --git a/ext/opcache/jit/zend_jit_internal.h b/ext/opcache/jit/zend_jit_internal.h
index 2007f28e91fd2..00f66676f39fd 100644
--- a/ext/opcache/jit/zend_jit_internal.h
+++ b/ext/opcache/jit/zend_jit_internal.h
@@ -231,6 +231,7 @@ ZEND_OPCODE_HANDLER_RET ZEND_FASTCALL zend_jit_loop_counter_helper(ZEND_OPCODE_H
 void ZEND_FASTCALL zend_jit_copy_extra_args_helper(EXECUTE_DATA_D);
 bool ZEND_FASTCALL zend_jit_deprecated_helper(OPLINE_D);
 void ZEND_FASTCALL zend_jit_undefined_long_key(EXECUTE_DATA_D);
+void ZEND_FASTCALL zend_jit_undefined_long_key_ex(zend_long key EXECUTE_DATA_DC);
 void ZEND_FASTCALL zend_jit_undefined_string_key(EXECUTE_DATA_D);
 
 zend_constant* ZEND_FASTCALL zend_jit_get_constant(const zval *key, uint32_t flags);
diff --git a/ext/opcache/jit/zend_jit_ir.c b/ext/opcache/jit/zend_jit_ir.c
index 4b31f2e07ae71..8d95ad5ea0c6c 100644
--- a/ext/opcache/jit/zend_jit_ir.c
+++ b/ext/opcache/jit/zend_jit_ir.c
@@ -3024,6 +3024,7 @@ static void zend_jit_setup_disasm(void)
 	REGISTER_HELPER(zend_jit_verify_return_slow);
 	REGISTER_HELPER(zend_jit_deprecated_helper);
 	REGISTER_HELPER(zend_jit_undefined_long_key);
+	REGISTER_HELPER(zend_jit_undefined_long_key_ex);
 	REGISTER_HELPER(zend_jit_undefined_string_key);
 	REGISTER_HELPER(zend_jit_copy_extra_args_helper);
 	REGISTER_HELPER(zend_jit_vm_stack_free_args_helper);
@@ -11716,6 +11717,7 @@ static int zend_jit_fetch_dimension_address_inner(zend_jit_ctx  *jit,
 					if (!op2_loaded) {
 						// JIT: hval = Z_LVAL_P(dim);
 						h = jit_Z_LVAL(jit, op2_addr);
+						op2_loaded = 1;
 					}
 					if (packed_loaded) {
 						ref = ir_CALL_2(IR_ADDR, ir_CONST_FC_FUNC(_zend_hash_index_find), ht_ref, h);
@@ -11765,6 +11767,7 @@ static int zend_jit_fetch_dimension_address_inner(zend_jit_ctx  *jit,
 					if (!op2_loaded) {
 						// JIT: hval = Z_LVAL_P(dim);
 						h = jit_Z_LVAL(jit, op2_addr);
+						op2_loaded = 1;
 					}
 					if (packed_loaded) {
 						ref = ir_CALL_2(IR_ADDR, ir_CONST_FC_FUNC(_zend_hash_index_find), ht_ref, h);
@@ -11808,7 +11811,19 @@ static int zend_jit_fetch_dimension_address_inner(zend_jit_ctx  *jit,
 							// JIT: zend_error(E_WARNING,"Undefined array key " ZEND_LONG_FMT, hval);
 							// JIT: retval = &EG(uninitialized_zval);
 							jit_SET_EX_OPLINE(jit, opline);
-							ir_CALL(IR_VOID, jit_STUB_FUNC_ADDR(jit, jit_stub_undefined_offset, IR_FASTCALL_FUNC));
+							if (Z_MODE(op2_addr) == IS_REG) {
+								if (!op2_loaded) {
+									// JIT: hval = Z_LVAL_P(dim);
+									h = jit_Z_LVAL(jit, op2_addr);
+								}
+								if (GCC_GLOBAL_REGS) {
+									ir_CALL_1(IR_VOID, ir_CONST_FC_FUNC(zend_jit_undefined_long_key_ex), h);
+								} else {
+									ir_CALL_2(IR_VOID, ir_CONST_FC_FUNC(zend_jit_undefined_long_key_ex), h, jit_FP(jit));
+								}
+							} else {
+								ir_CALL(IR_VOID, jit_STUB_FUNC_ADDR(jit, jit_stub_undefined_offset, IR_FASTCALL_FUNC));
+							}
 							ir_END_list(*end_inputs);
 							break;
 						case BP_VAR_IS:
diff --git a/ext/opcache/jit/zend_jit_vm_helpers.c b/ext/opcache/jit/zend_jit_vm_helpers.c
index e9cdeeab9865a..d93e5fce94780 100644
--- a/ext/opcache/jit/zend_jit_vm_helpers.c
+++ b/ext/opcache/jit/zend_jit_vm_helpers.c
@@ -210,6 +210,15 @@ void ZEND_FASTCALL zend_jit_undefined_long_key(EXECUTE_DATA_D)
 	ZVAL_NULL(result);
 }
 
+void ZEND_FASTCALL zend_jit_undefined_long_key_ex(zend_long key EXECUTE_DATA_DC)
+{
+	const zend_op *opline = EX(opline);
+	zval *result = EX_VAR(opline->result.var);
+
+	zend_error(E_WARNING, "Undefined array key " ZEND_LONG_FMT, key);
+	ZVAL_NULL(result);
+}
+
 void ZEND_FASTCALL zend_jit_undefined_string_key(EXECUTE_DATA_D)
 {
 	const zend_op *opline = EX(opline);
diff --git a/ext/opcache/tests/jit/gh15972.phpt b/ext/opcache/tests/jit/gh15972.phpt
new file mode 100644
index 0000000000000..11d234f0c96a5
--- /dev/null
+++ b/ext/opcache/tests/jit/gh15972.phpt
@@ -0,0 +1,16 @@
+--TEST--
+GH-15972 (Assertion failure in ext/opcache/jit/zend_jit_vm_helpers.c with function JIT)
+--EXTENSIONS--
+opcache
+--FILE--
+<?php
+function test(){
+for($i = 0; $i < 2; $i++){
+$a = @[3][$i];
+}
+}
+test();
+?>
+DONE
+--EXPECT--
+DONE