diff --git a/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt b/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt
index c0553397..6da0b407 100644
--- a/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt
+++ b/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt
@@ -93,6 +93,8 @@ internal fun BigDecimal.factorial(): BigDecimal {
     if (this < BigDecimal.ZERO) throw ExpressionException.FactorialCalculation()
     if (this > maxFactorial) throw ExpressionException.TooBig()
 
+    if (this.compareTo(BigDecimal.ZERO) == 0) return BigDecimal.ONE
+
     var expr = this
     for (i in 1 until this.toInt()) {
         expr *= BigDecimal(i)
diff --git a/data/evaluatto/src/test/java/io/github/sadellie/evaluatto/ExpressionSimpleTest.kt b/data/evaluatto/src/test/java/io/github/sadellie/evaluatto/ExpressionSimpleTest.kt
index e394f36b..03419438 100644
--- a/data/evaluatto/src/test/java/io/github/sadellie/evaluatto/ExpressionSimpleTest.kt
+++ b/data/evaluatto/src/test/java/io/github/sadellie/evaluatto/ExpressionSimpleTest.kt
@@ -108,4 +108,7 @@ class ExpressionSimpleTest {
 
     @Test
     fun expression28() = assertExpr("e", "2.7182818285")
+
+    @Test
+    fun expression29() = assertExpr("0!", "1")
 }