diff --git a/NEWS b/NEWS
index fa4018bf8ed..404290dcf61 100644
--- a/NEWS
+++ b/NEWS
@@ -15,6 +15,7 @@ PHP                                                                        NEWS
 - Opcache:
   . Fixed bug GH-15834 (Segfault with hook "simple get" cache slot and minimal
     JIT). (nielsdos)
+  . Fixed bug GH-17966 (Symfony JIT 1205 assertion failure). (nielsdos)
 
 - Standard:
   . Fix memory leaks in array_any() / array_all(). (nielsdos)
diff --git a/ext/opcache/tests/jit/gh17966.phpt b/ext/opcache/tests/jit/gh17966.phpt
new file mode 100644
index 00000000000..f9983ad4c2b
--- /dev/null
+++ b/ext/opcache/tests/jit/gh17966.phpt
@@ -0,0 +1,25 @@
+--TEST--
+GH-17966 (Symfony JIT 1205 assertion failure)
+--EXTENSIONS--
+opcache
+--INI--
+opcache.jit=1205
+--FILE--
+<?php
+function test($value, bool $test)
+{
+    $value = (float) $value;
+
+    if ($test) {
+        return $value * 2;
+    }
+
+    return $value;
+}
+
+var_dump(test(1.25, true));
+var_dump(test(1.25, false));
+?>
+--EXPECT--
+float(2.5)
+float(1.25)