diff --git a/Zend/tests/bug72943.phpt b/Zend/tests/bug72943.phpt
new file mode 100644
index 00000000000..8bab6de4564
--- /dev/null
+++ b/Zend/tests/bug72943.phpt
@@ -0,0 +1,20 @@
+--TEST--
+Bug #72943 (assign_dim on string doesn't reset hval)
+--FILE--
+<?php
+$array = array("test" => 1);
+
+$a = "lest";
+var_dump($array[$a]);
+$a[0] = "f";
+var_dump($array[$a]);
+$a[0] = "t";
+var_dump($array[$a]);
+?>
+--EXPECTF--
+Notice: Undefined index: lest in %sbug72943.php on line %d
+NULL
+
+Notice: Undefined index: fest in %sbug72943.php on line %d
+NULL
+int(1)
diff --git a/Zend/zend_execute.c b/Zend/zend_execute.c
index d2411ad5c3b..f0f249e2434 100644
--- a/Zend/zend_execute.c
+++ b/Zend/zend_execute.c
@@ -1330,6 +1330,7 @@ static zend_never_inline void zend_assign_to_string_offset(zval *str, zval *dim,
 		zend_string_release(old_str);
 	} else {
 		SEPARATE_STRING(str);
+		zend_string_forget_hash_val(Z_STR_P(str));
 	}
 
 	Z_STRVAL_P(str)[offset] = c;