diff --git a/tinyexpr.c b/tinyexpr.c
index 914a950..2f828c2 100644
--- a/tinyexpr.c
+++ b/tinyexpr.c
@@ -130,7 +130,11 @@ static double add(double a, double b) {return a + b;}
 static double sub(double a, double b) {return a - b;}
 static double mul(double a, double b) {return a * b;}
 static double divide(double a, double b) {return a / b;}
-static double mod(double a, double b) {return ((long long)b) ? ((long long)a % (long long)b) : (0.0/0.0);}
+static double mod(double a, double b) {
+    if (a!=a || b!=b) return 0.0/0.0;
+    if (((long long)b) == 0) return 0.0/0.0;
+    return ((long long)a % (long long)b);
+}
 static double negate(double a) {return -a;}