diff --git a/NEWS b/NEWS
index 103b778aacf4..8b01cda2e84f 100644
--- a/NEWS
+++ b/NEWS
@@ -57,6 +57,10 @@ PHP                                                                        NEWS
 - PHPDBG:
   . Fixed bug GH-16174 (Empty string is an invalid expression for ev). (cmb)
 
+- Reflection:
+  . Fixed bug GH-15902 (Core dumped in ext/reflection/php_reflection.c).
+    (DanielEScherzer)
+
 - Session:
   . Fixed bug GH-16385 (Unexpected null returned by session_set_cookie_params).
     (nielsdos)
diff --git a/ext/reflection/php_reflection.c b/ext/reflection/php_reflection.c
index 3faf8ed78681..88ca1cd63424 100644
--- a/ext/reflection/php_reflection.c
+++ b/ext/reflection/php_reflection.c
@@ -639,13 +639,19 @@ static int format_default_value(smart_str *str, zval *value) {
 		} ZEND_HASH_FOREACH_END();
 		smart_str_appendc(str, ']');
 	} else if (Z_TYPE_P(value) == IS_OBJECT) {
-		/* This branch may only be reached for default properties, which don't support arbitrary objects. */
+		/* This branch may only be reached for default properties; show enum names,
+			or the type of non-enums (GH-15902) */
 		zend_object *obj = Z_OBJ_P(value);
 		zend_class_entry *class = obj->ce;
-		ZEND_ASSERT(class->ce_flags & ZEND_ACC_ENUM);
-		smart_str_append(str, class->name);
-		smart_str_appends(str, "::");
-		smart_str_append(str, Z_STR_P(zend_enum_fetch_case_name(obj)));
+		if (class->ce_flags & ZEND_ACC_ENUM) {
+			smart_str_append(str, class->name);
+			smart_str_appends(str, "::");
+			smart_str_append(str, Z_STR_P(zend_enum_fetch_case_name(obj)));
+		} else {
+			smart_str_appends(str, "object(");
+			smart_str_append(str, class->name);
+			smart_str_appends(str, ")");
+		}
 	} else {
 		ZEND_ASSERT(Z_TYPE_P(value) == IS_CONSTANT_AST);
 		zend_string *ast_str = zend_ast_export("", Z_ASTVAL_P(value), "");
@@ -878,7 +884,10 @@ static zval *property_get_default(zend_property_info *prop_info) {
 		ZVAL_DEINDIRECT(prop);
 		return prop;
 	} else {
-		return &ce->default_properties_table[OBJ_PROP_TO_NUM(prop_info->offset)];
+		if (UNEXPECTED(zend_update_class_constants(ce) != SUCCESS)) {
+			return &EG(uninitialized_zval);
+		}
+		return &CE_DEFAULT_PROPERTIES_TABLE(ce)[OBJ_PROP_TO_NUM(prop_info->offset)];
 	}
 }
 
diff --git a/ext/reflection/tests/gh15902/ReflectionClass-callable.phpt b/ext/reflection/tests/gh15902/ReflectionClass-callable.phpt
new file mode 100644
index 000000000000..62669554b245
--- /dev/null
+++ b/ext/reflection/tests/gh15902/ReflectionClass-callable.phpt
@@ -0,0 +1,36 @@
+--TEST--
+ReflectionClass object default property - used to say "callable"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+define('FOO', new stdClass);
+
+new C;
+
+$reflector = new ReflectionClass(C::class);
+var_dump( (string)$reflector );
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-callable.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = object(stdClass) ]
+  }
+
+  - Methods [0] {
+  }
+}
+"
diff --git a/ext/reflection/tests/gh15902/ReflectionClass-class.phpt b/ext/reflection/tests/gh15902/ReflectionClass-class.phpt
new file mode 100644
index 000000000000..e95d50123f0f
--- /dev/null
+++ b/ext/reflection/tests/gh15902/ReflectionClass-class.phpt
@@ -0,0 +1,37 @@
+--TEST--
+ReflectionClass object default property - used to say "__CLASS__"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionClass(C::class);
+
+define('FOO', new stdClass);
+new C;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Class [ <user> class C ] {
+  @@ %sReflectionClass-class.php %d-%d
+
+  - Constants [0] {
+  }
+
+  - Static properties [0] {
+  }
+
+  - Static methods [0] {
+  }
+
+  - Properties [1] {
+    Property [ public stdClass $a = object(stdClass) ]
+  }
+
+  - Methods [0] {
+  }
+}
+"
diff --git a/ext/reflection/tests/gh15902/ReflectionProperty-callable.phpt b/ext/reflection/tests/gh15902/ReflectionProperty-callable.phpt
new file mode 100644
index 000000000000..64402f1bfe60
--- /dev/null
+++ b/ext/reflection/tests/gh15902/ReflectionProperty-callable.phpt
@@ -0,0 +1,19 @@
+--TEST--
+ReflectionProperty object default - used to say "callable"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+define('FOO', new stdClass);
+
+new C;
+
+$reflector = new ReflectionProperty(C::class, 'a');
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = object(stdClass) ]
+"
diff --git a/ext/reflection/tests/gh15902/ReflectionProperty-class.phpt b/ext/reflection/tests/gh15902/ReflectionProperty-class.phpt
new file mode 100644
index 000000000000..454403f9eeca
--- /dev/null
+++ b/ext/reflection/tests/gh15902/ReflectionProperty-class.phpt
@@ -0,0 +1,19 @@
+--TEST--
+ReflectionProperty object default - used to say "__CLASS__"
+--FILE--
+<?php
+
+class C {
+	public stdClass $a = FOO;
+}
+$reflector = new ReflectionProperty(C::class, 'a');
+
+define('FOO', new stdClass);
+new C;
+
+var_dump( (string)$reflector );
+
+?>
+--EXPECTF--
+string(%d) "Property [ public stdClass $a = object(stdClass) ]
+"