diff --git a/pkg/expression/builtin_cast.go b/pkg/expression/builtin_cast.go
index e47124282d5c0..4ca799994736f 100644
--- a/pkg/expression/builtin_cast.go
+++ b/pkg/expression/builtin_cast.go
@@ -880,7 +880,7 @@ func (b *builtinCastStringAsJSONSig) evalJSON(row chunk.Row) (res types.BinaryJS
 	typ := b.args[0].GetType()
 	if types.IsBinaryStr(typ) {
 		buf := []byte(val)
-		if typ.GetType() == mysql.TypeString {
+		if typ.GetType() == mysql.TypeString && typ.GetFlen() > 0 {
 			// the tailing zero should also be in the opaque json
 			buf = make([]byte, typ.GetFlen())
 			copy(buf, val)
diff --git a/pkg/expression/builtin_cast_vec.go b/pkg/expression/builtin_cast_vec.go
index d4df1f3b60cae..c414375e62601 100644
--- a/pkg/expression/builtin_cast_vec.go
+++ b/pkg/expression/builtin_cast_vec.go
@@ -844,7 +844,7 @@ func (b *builtinCastStringAsJSONSig) vecEvalJSON(input *chunk.Chunk, result *chu
 
 			val := buf.GetBytes(i)
 			resultBuf := val
-			if typ.GetType() == mysql.TypeString {
+			if typ.GetType() == mysql.TypeString && typ.GetFlen() > 0 {
 				// only for BINARY: the tailing zero should also be in the opaque json
 				resultBuf = make([]byte, typ.GetFlen())
 				copy(resultBuf, val)
diff --git a/tests/integrationtest/r/expression/json.result b/tests/integrationtest/r/expression/json.result
index 8a1472456f31d..d2ad35eb6ee30 100644
--- a/tests/integrationtest/r/expression/json.result
+++ b/tests/integrationtest/r/expression/json.result
@@ -602,3 +602,24 @@ json_extract('[{"a": [1,2,3,4]}]', '$[0].a[0 to last]')
 select json_extract('[{"a": [1,2,3,4]}]', '$[0].a[0 to 2]');
 json_extract('[{"a": [1,2,3,4]}]', '$[0].a[0 to 2]')
 [1, 2, 3]
+select cast(binary 'aa' as json);
+cast(binary 'aa' as json)
+"base64:type254:YWE="
+drop table if exists t;
+create table t (vb VARBINARY(10), b BINARY(10), vc VARCHAR(10), c CHAR(10));
+insert into t values ('1', '1', '1', '1');
+select cast(vb as json), cast(b as json), cast(vc as json), cast(c as json) from t;
+cast(vb as json)	cast(b as json)	cast(vc as json)	cast(c as json)
+"base64:type15:MQ=="	"base64:type254:MQAAAAAAAAAAAA=="	1	1
+select 1 from t where cast(vb as json) = '1';
+1
+select 1 from t where cast(b as json) = '1';
+1
+select 1 from t where cast(vc as json) = '1';
+1
+select 1 from t where cast(c as json) = '1';
+1
+select 1 from t where cast(BINARY vc as json) = '1';
+1
+select 1 from t where cast(BINARY c as json) = '1';
+1
diff --git a/tests/integrationtest/t/expression/json.test b/tests/integrationtest/t/expression/json.test
index ca41e0b701fea..a7b613438623c 100644
--- a/tests/integrationtest/t/expression/json.test
+++ b/tests/integrationtest/t/expression/json.test
@@ -359,3 +359,15 @@ select json_extract('[{"a": [1,2,3,4]}]', '$[0].a[1 to 100]');
 select json_extract('[{"a": [1,2,3,4]}]', '$[0].a[0 to last]');
 select json_extract('[{"a": [1,2,3,4]}]', '$[0].a[0 to 2]');
 
+# TestCastBinaryStringToJSON
+select cast(binary 'aa' as json);
+drop table if exists t;
+create table t (vb VARBINARY(10), b BINARY(10), vc VARCHAR(10), c CHAR(10));
+insert into t values ('1', '1', '1', '1');
+select cast(vb as json), cast(b as json), cast(vc as json), cast(c as json) from t;
+select 1 from t where cast(vb as json) = '1';
+select 1 from t where cast(b as json) = '1';
+select 1 from t where cast(vc as json) = '1';
+select 1 from t where cast(c as json) = '1';
+select 1 from t where cast(BINARY vc as json) = '1';
+select 1 from t where cast(BINARY c as json) = '1';