diff --git a/src/lib/string.ts b/src/lib/string.ts
index 587649a..d2cc0d1 100644
--- a/src/lib/string.ts
+++ b/src/lib/string.ts
@@ -4,12 +4,12 @@ import { LuaError } from '../LuaError'
 import {
     tostring,
     posrelat,
-    coerceArgToNumber,
-    coerceArgToString,
-    hasOwnProperty,
-    LuaType,
-    coerceToBoolean
-} from '../utils'
+    coerceArgToNumber,
+    coerceArgToString,
+    hasOwnProperty,
+    LuaType,
+    coerceArgToBoolean
+} from '../utils'
 
 const ROSETTA_STONE: Record<string, string> = {
     '([^a-zA-Z0-9%(])-': '$1*?',
@@ -125,7 +125,7 @@ function find(s: LuaType, pattern: LuaType, init: LuaType, plain: LuaType): (num
     const S = coerceArgToString(s, 'find', 1)
     const P = coerceArgToString(pattern, 'find', 2)
     const INIT = init === undefined ? 1 : coerceArgToNumber(init, 'find', 3)
-    const PLAIN = plain === undefined ? false : coerceToBoolean(plain)
+    const PLAIN = plain === undefined ? false : coerceArgToBoolean(plain, 'find', 4)
 
     // Regex
     if (!PLAIN) {
diff --git a/src/utils.ts b/src/utils.ts
index 7f565b4..eb29d52 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -157,23 +157,27 @@ function coerceToString(val: LuaType, errorMessage?: string): string {
     throwCoerceError(val, errorMessage)
 }
 
-function coerceArg<T>(
-    value: LuaType,
-    coerceFunc: (val: LuaType, errorMessage?: string) => T,
-    typ: 'number' | 'string',
-    funcName: string,
-    index: number
-): T {
-    return coerceFunc(value, `bad argument #${index} to '${funcName}' (${typ} expected, got %type)`)
-}
-
-function coerceArgToNumber(value: LuaType, funcName: string, index: number): number {
-    return coerceArg<number>(value, coerceToNumber, 'number', funcName, index)
-}
-
-function coerceArgToString(value: LuaType, funcName: string, index: number): string {
-    return coerceArg<string>(value, coerceToString, 'string', funcName, index)
-}
+function coerceArg<T>(
+    value: LuaType,
+    coerceFunc: (val: LuaType, errorMessage?: string) => T,
+    typ: 'number' | 'string' | 'boolean',
+    funcName: string,
+    index: number
+): T {
+    return coerceFunc(value, `bad argument #${index} to '${funcName}' (${typ} expected, got %type)`)
+}
+
+function coerceArgToNumber(value: LuaType, funcName: string, index: number): number {
+    return coerceArg<number>(value, coerceToNumber, 'number', funcName, index)
+}
+
+function coerceArgToString(value: LuaType, funcName: string, index: number): string {
+    return coerceArg<string>(value, coerceToString, 'string', funcName, index)
+}
+
+function coerceArgToBoolean(value: LuaType, funcName: string, index: number): boolean {
+    return coerceArg<boolean>(value, coerceToBoolean, 'boolean', funcName, index)
+}
 
 function coerceArgToTable(value: LuaType, funcName: string, index: number): Table {
     if (value instanceof Table) {
@@ -203,14 +207,15 @@ export {
     Config,
     type,
     tostring,
-    posrelat,
-    coerceToBoolean,
-    coerceToNumber,
-    coerceToString,
-    coerceArgToNumber,
-    coerceArgToString,
-    coerceArgToTable,
-    coerceArgToFunction,
-    ensureArray,
-    hasOwnProperty
-}
+    posrelat,
+    coerceToBoolean,
+    coerceToNumber,
+    coerceToString,
+    coerceArgToBoolean,
+    coerceArgToNumber,
+    coerceArgToString,
+    coerceArgToTable,
+    coerceArgToFunction,
+    ensureArray,
+    hasOwnProperty
+}