diff --git a/src/engine.ts b/src/engine.ts
index fbf8b68..2edcae6 100644
--- a/src/engine.ts
+++ b/src/engine.ts
@@ -3,7 +3,7 @@ import { JsonTemplateLexer } from './lexer';
 import { JsonTemplateParser } from './parser';
 import { JsonTemplateReverseTranslator } from './reverse_translator';
 import { JsonTemplateTranslator } from './translator';
-import { EngineOptions, Expression, FlatMappingPaths } from './types';
+import { EngineOptions, Expression, FlatMappingPaths, TemplateInput } from './types';
 import { CreateAsyncFunction, convertToObjectMapping, isExpression } from './utils';
 
 export class JsonTemplateEngine {
@@ -21,10 +21,7 @@ export class JsonTemplateEngine {
     return Function(DATA_PARAM_KEY, BINDINGS_PARAM_KEY, this.translate(templateOrExpr, options));
   }
 
-  private static compileAsAsync(
-    templateOrExpr: string | Expression | FlatMappingPaths[],
-    options?: EngineOptions,
-  ): Function {
+  private static compileAsAsync(templateOrExpr: TemplateInput, options?: EngineOptions): Function {
     return CreateAsyncFunction(
       DATA_PARAM_KEY,
       BINDINGS_PARAM_KEY,
@@ -49,10 +46,7 @@ export class JsonTemplateEngine {
     return convertToObjectMapping(flatMappingAST);
   }
 
-  static create(
-    templateOrExpr: string | Expression | FlatMappingPaths[],
-    options?: EngineOptions,
-  ): JsonTemplateEngine {
+  static create(templateOrExpr: TemplateInput, options?: EngineOptions): JsonTemplateEngine {
     return new JsonTemplateEngine(this.compileAsAsync(templateOrExpr, options));
   }
 
@@ -63,10 +57,7 @@ export class JsonTemplateEngine {
     return new JsonTemplateEngine(this.compileAsSync(templateOrExpr, options));
   }
 
-  static parse(
-    template: string | Expression | FlatMappingPaths[],
-    options?: EngineOptions,
-  ): Expression {
+  static parse(template: TemplateInput, options?: EngineOptions): Expression {
     if (isExpression(template)) {
       return template as Expression;
     }
@@ -78,10 +69,7 @@ export class JsonTemplateEngine {
     return this.parseMappingPaths(template as FlatMappingPaths[], options);
   }
 
-  static translate(
-    template: string | Expression | FlatMappingPaths[],
-    options?: EngineOptions,
-  ): string {
+  static translate(template: TemplateInput, options?: EngineOptions): string {
     return this.translateExpression(this.parse(template, options));
   }
 
diff --git a/src/parser.ts b/src/parser.ts
index 73041c4..e673fc6 100644
--- a/src/parser.ts
+++ b/src/parser.ts
@@ -1,3 +1,4 @@
+/* eslint-disable import/no-cycle */
 import { BINDINGS_PARAM_KEY, DATA_PARAM_KEY, EMPTY_EXPR } from './constants';
 import { JsonTemplateEngine } from './engine';
 import { JsonTemplateLexerError, JsonTemplateParserError } from './errors';
@@ -305,7 +306,7 @@ export class JsonTemplateParser {
     }
     return {
       pathType: PathType.UNKNOWN,
-      inferredPathType: this.options?.defaultPathType || PathType.RICH,
+      inferredPathType: this.options?.defaultPathType ?? PathType.RICH,
     };
   }
 
diff --git a/src/translator.ts b/src/translator.ts
index f3add5f..1d90e16 100644
--- a/src/translator.ts
+++ b/src/translator.ts
@@ -509,7 +509,7 @@ export class JsonTemplateTranslator {
       code.push(`if(${functionName} && typeof ${functionName} === 'function'){`);
       code.push(result, '=', functionName, '(', functionArgsStr, ');');
       code.push('} else {');
-      code.push(result, '=', expr.id, '(', expr.parent || result, ',', functionArgsStr, ');');
+      code.push(result, '=', expr.id, '(', expr.parent ?? result, ',', functionArgsStr, ');');
       code.push('}');
     } else {
       code.push(result, '=', functionName, '(', functionArgsStr, ');');
diff --git a/src/types.ts b/src/types.ts
index 53c283f..ecd16d8 100644
--- a/src/types.ts
+++ b/src/types.ts
@@ -283,3 +283,5 @@ export type FlatMappingAST = FlatMappingPaths & {
   inputExpr: PathExpression;
   outputExpr: PathExpression;
 };
+
+export type TemplateInput = string | Expression | FlatMappingPaths[];