diff --git a/ext/opcache/jit/zend_jit.c b/ext/opcache/jit/zend_jit.c
index 19e5520b1569e..da73c98c43552 100644
--- a/ext/opcache/jit/zend_jit.c
+++ b/ext/opcache/jit/zend_jit.c
@@ -2748,7 +2748,7 @@ static int zend_jit(const zend_op_array *op_array, zend_ssa *ssa, const zend_op
 					if (i == end
 					 && (opline->result_type & (IS_SMART_BRANCH_JMPZ|IS_SMART_BRANCH_JMPNZ)) != 0) {
 						/* smart branch split across basic blocks */
-						if (!zend_jit_set_cond(&ctx, opline + 2, opline->result.var)) {
+						if (!zend_jit_set_cond(&ctx, opline, opline + 2, opline->result.var)) {
 							goto jit_failure;
 						}
 					}
diff --git a/ext/opcache/jit/zend_jit_ir.c b/ext/opcache/jit/zend_jit_ir.c
index 2bad605c537d0..4251d6b891c94 100644
--- a/ext/opcache/jit/zend_jit_ir.c
+++ b/ext/opcache/jit/zend_jit_ir.c
@@ -4105,11 +4105,12 @@ static int zend_jit_cond_jmp(zend_jit_ctx *jit, const zend_op *next_opline, int
 	return 1;
 }
 
-static int zend_jit_set_cond(zend_jit_ctx *jit, const zend_op *next_opline, uint32_t var)
+static int zend_jit_set_cond(zend_jit_ctx *jit, const zend_op *opline, const zend_op *next_opline, uint32_t var)
 {
 	ir_ref ref;
 
-	ref = ir_ADD_U32(ir_ZEXT_U32(jit_CMP_IP(jit, IR_EQ, next_opline)), ir_CONST_U32(IS_FALSE));
+	ir_op op = (opline->result_type & IS_SMART_BRANCH_JMPZ) ? IR_EQ : IR_NE;
+	ref = ir_ADD_U32(ir_ZEXT_U32(jit_CMP_IP(jit, op, next_opline)), ir_CONST_U32(IS_FALSE));
 
 	// EX_VAR(var) = ...
 	ir_STORE(ir_ADD_OFFSET(jit_FP(jit), var + offsetof(zval, u1.type_info)), ref);
diff --git a/ext/opcache/tests/jit/gh21593.phpt b/ext/opcache/tests/jit/gh21593.phpt
new file mode 100644
index 0000000000000..d37500195737d
--- /dev/null
+++ b/ext/opcache/tests/jit/gh21593.phpt
@@ -0,0 +1,49 @@
+--TEST--
+GH-21593: Function JIT JMPNZ smart branch
+--CREDITS--
+paulmhh
+--EXTENSIONS--
+opcache
+--INI--
+opcache.enable=1
+opcache.enable_cli=1
+opcache.jit=function
+--FILE--
+<?php
+
+function test1($a) {
+    if (isset($a?->a)) {
+        echo "1\n";
+    }
+}
+
+function test2($a) {
+    if (!isset($a?->a)) {
+        echo "2\n";
+    }
+}
+
+function test3($a) {
+    if (empty($a?->a)) {
+        echo "3\n";
+    }
+}
+
+function test4($a) {
+    if (!empty($a?->a)) {
+        echo "4\n";
+    }
+}
+
+$a = new stdClass;
+$a->a = 'a';
+
+test1($a);
+test2($a);
+test3($a);
+test4($a);
+
+?>
+--EXPECT--
+1
+4