diff --git a/ext/opcache/jit/zend_jit_ir.c b/ext/opcache/jit/zend_jit_ir.c
index 92a068dbfaca..84e1e668e63d 100644
--- a/ext/opcache/jit/zend_jit_ir.c
+++ b/ext/opcache/jit/zend_jit_ir.c
@@ -1398,7 +1398,9 @@ static void zend_jit_def_reg(zend_jit_ctx *jit, zend_jit_addr addr, ir_ref val)
 			if (dst_phi->pi >= 0) {
 				jit->ra[src_var].ref = val;
 				src_var = dst_phi->ssa_var;
-				if (!(jit->ra[src_var].flags & ZREG_FORWARD)) {
+				if (!(jit->ra[src_var].flags & ZREG_FORWARD)
+				 /* Pi in a block that is not generated yet. It forwards later on its own. */
+				 || (jit->bb_start_ref && !jit->bb_start_ref[dst_phi->block])) {
 					phi = zend_ssa_next_use_phi(jit->ssa, var, phi);
 					continue;
 				}
diff --git a/ext/opcache/tests/jit/gh24396.phpt b/ext/opcache/tests/jit/gh24396.phpt
new file mode 100644
index 000000000000..0ad5696b208f
--- /dev/null
+++ b/ext/opcache/tests/jit/gh24396.phpt
@@ -0,0 +1,22 @@
+--TEST--
+GH-24396: Assertion failure in zend_jit_def_reg() "reg forwarding" with chained Pi nodes
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.file_update_protection=0
+opcache.jit=function
+--FILE--
+<?php
+function f() {
+    $i = 0;
+    do {
+        $i = ($i + 1) & 255;
+    } while ($i < 2 || $i > 200);
+    return $i;
+}
+var_dump(f());
+?>
+--EXPECT--
+int(2)