diff --git a/src/main/java/com/greplin/interval/NumericIntervalField.java b/src/main/java/com/greplin/interval/NumericIntervalField.java
index 655429d..ef5f1a3 100644
--- a/src/main/java/com/greplin/interval/NumericIntervalField.java
+++ b/src/main/java/com/greplin/interval/NumericIntervalField.java
@@ -118,9 +118,13 @@ public TokenStream tokenStreamValue() {
   static long[] splitParts(final String rangeString) {
     String trimmed = rangeString.trim();
     int middle = trimmed.indexOf('-', 1);
-    long start = Long.parseLong(trimmed.substring(0, middle).trim());
-    long end = Long.parseLong(trimmed.substring(middle + 1).trim());
-    return new long[]{start, end};
+    try {
+        long start = Long.parseLong(trimmed.substring(0, middle).trim());
+        long end = Long.parseLong(trimmed.substring(middle + 1).trim());
+        return new long[]{start, end};
+    } catch (NumberFormatException e) {
+        throw new NumberFormatException("Passed value does not contain two parsable long values");
+    }
   }
 
   /**
diff --git a/src/test/java/com/greplin/interval/NumericIntervalFieldTest.java b/src/test/java/com/greplin/interval/NumericIntervalFieldTest.java
index b9c24b9..170fd7d 100644
--- a/src/test/java/com/greplin/interval/NumericIntervalFieldTest.java
+++ b/src/test/java/com/greplin/interval/NumericIntervalFieldTest.java
@@ -54,4 +54,9 @@ public void testSplitParts() {
 
     Assert.assertArrayEquals(new long[]{-100, 21253456}, NumericIntervalField.splitParts("-100-21253456"));
   }
+
+  @Test (expected=NumberFormatException.class)
+  public void testEmptyNumbers() throws Exception {
+    long[] result = NumericIntervalField.splitParts("null-null");
+  }
 }