diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index ce4e9d60..480b33f3 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -10,6 +10,7 @@
 * Fix sebeolsik-3sin-p2 '"' character [#509](https://github.com/Riey/kime/issues/509)
 * Fix sebeolsik-391 "S-F" key [#521](https://github.com/Riey/kime/issues/521)
 * Don't compose choseong when FlexibleComposeOrder is on [#520](https://github.com/Riey/kime/issues/520)
+* Fix choseong converted into jongseong even `TreatJongseongAsChoseong` is off [#529](https://github.com/Riey/kime/issues/529)
 
 ## 2.5.5
 
diff --git a/src/engine/backends/hangul/src/state.rs b/src/engine/backends/hangul/src/state.rs
index b27fc8c2..470e3586 100644
--- a/src/engine/backends/hangul/src/state.rs
+++ b/src/engine/backends/hangul/src/state.rs
@@ -374,6 +374,14 @@ impl CharacterState {
                     ..Default::default()
                 }),
             }
+        } else if let Some(_) = self.jong {
+            // $ㅁ + ㅏ = ㅁㅏ
+            // 초성없이 중성과 종성만 있는 경우를 배제
+            CharacterResult::NewCharacter(Self {
+                jung: Some(jung),
+                compose_jung,
+                ..Default::default()
+            })
         } else {
             self.jung = Some(jung);
             self.compose_jung = compose_jung;
@@ -391,19 +399,26 @@ impl CharacterState {
                 None => {
                     let new;
 
-                    match jong.to_cho(addons) {
-                        JongToCho::Direct(cho) => {
-                            new = Self {
-                                cho: Some(cho),
-                                ..Default::default()
-                            };
-                        }
-                        JongToCho::Compose(..) => {
-                            new = Self {
-                                jong: Some(jong),
-                                ..Default::default()
-                            };
+                    if addons.contains(Addon::TreatJongseongAsChoseong) {
+                        match jong.to_cho(addons) {
+                            JongToCho::Direct(cho) => {
+                                new = Self {
+                                    cho: Some(cho),
+                                    ..Default::default()
+                                };
+                            }
+                            JongToCho::Compose(..) => {
+                                new = Self {
+                                    jong: Some(jong),
+                                    ..Default::default()
+                                };
+                            }
                         }
+                    } else {
+                        new = Self {
+                            jong: Some(jong),
+                            ..Default::default()
+                        };
                     }
 
                     CharacterResult::NewCharacter(new)
diff --git a/src/engine/core/tests/sebeolsik_3_90.rs b/src/engine/core/tests/sebeolsik_3_90.rs
index 94de7a0d..02045d01 100644
--- a/src/engine/core/tests/sebeolsik_3_90.rs
+++ b/src/engine/core/tests/sebeolsik_3_90.rs
@@ -15,6 +15,18 @@ fn hello() {
     ]);
 }
 
+// issue #529
+#[test]
+fn dont_convert_jongseong() {
+    test_input(&[
+        (Key::normal(K), "ㄱ", ""),
+        (Key::normal(F), "가", ""),
+        (Key::normal(Z), "감", ""),
+        (Key::normal(Z), "ㅁ", "감"),
+        (Key::normal(F), "ㅏ", "ㅁ"),
+    ]);
+}
+
 // issue #263
 #[test]
 fn compose_choseong_ssang() {
@@ -24,7 +36,7 @@ fn compose_choseong_ssang() {
         (Key::normal(X), "각", ""),
         (Key::normal(K), "ㄱ", "각"),
         (Key::normal(D), "기", ""),
-    ])
+    ]);
 }
 
 #[test]
diff --git a/src/engine/core/tests/shared.rs b/src/engine/core/tests/shared.rs
index 43b85576..b049962e 100644
--- a/src/engine/core/tests/shared.rs
+++ b/src/engine/core/tests/shared.rs
@@ -29,11 +29,7 @@ pub fn test_input_impl(engine: EngineConfig, category: InputCategory, keys: &[(K
 
         eprintln!("Ret: {:?}", ret);
 
-        if ret.contains(InputResult::HAS_PREEDIT) {
-            test_preedit!(preedit);
-        } else {
-            assert!(preedit.is_empty());
-        }
+        test_preedit!(preedit);
 
         if ret.contains(InputResult::HAS_COMMIT) {
             if ret.contains(InputResult::CONSUMED) {