diff --git a/src/time_unit/mod.rs b/src/time_unit/mod.rs
index b3d19c2..1a89cd0 100644
--- a/src/time_unit/mod.rs
+++ b/src/time_unit/mod.rs
@@ -297,6 +297,7 @@ where
     fn ordinals_from_root_specifier(root_specifier: &RootSpecifier) -> Result<OrdinalSet, Error> {
         let ordinals = match root_specifier {
             RootSpecifier::Specifier(specifier) => Self::ordinals_from_specifier(specifier)?,
+            RootSpecifier::Period(_, 0) => Err(ErrorKind::Expression(format!("range step cannot be zero")))?,
             RootSpecifier::Period(start, step) => {
                 let base_set = match start {
                     // A point prior to a period implies a range whose start is the specified
diff --git a/tests/lib.rs b/tests/lib.rs
index e4270df..7b8091b 100644
--- a/tests/lib.rs
+++ b/tests/lib.rs
@@ -221,6 +221,12 @@ mod tests {
         );
     }
 
+    #[test]
+    fn test_invalid_step() {
+        let expression = "0/0 * * * *";
+        assert!(Schedule::from_str(expression).is_err());
+    }
+
     #[test]
     fn test_time_unit_spec_years() {
         let expression = "* * * * * * 2015-2044";