diff --git a/src/main/java/io/split/android/client/validators/FlagSetsValidatorImpl.java b/src/main/java/io/split/android/client/validators/FlagSetsValidatorImpl.java
index 550342bc3..72daeb055 100644
--- a/src/main/java/io/split/android/client/validators/FlagSetsValidatorImpl.java
+++ b/src/main/java/io/split/android/client/validators/FlagSetsValidatorImpl.java
@@ -9,7 +9,7 @@
 
 public class FlagSetsValidatorImpl implements SplitFilterValidator {
 
-    private static final String FLAG_SET_REGEX = "^[a-z][_a-z0-9]{0,49}$";
+    private static final String FLAG_SET_REGEX = "^[a-z0-9][_a-z0-9]{0,49}$";
 
     /**
      * Validates the flag sets and returns a list of
@@ -30,11 +30,16 @@ public List<String> cleanup(List<String> values) {
                 continue;
             }
 
-            if (set.startsWith(" ") || set.endsWith(" ")) {
+            if (set.trim().length() != set.length()) {
                 Logger.w("SDK config: Flag Set name " + set + " has extra whitespace, trimming");
                 set = set.trim();
             }
 
+            if (!set.toLowerCase().equals(set)) {
+                Logger.w("SDK config: Flag Set name "+set+" should be all lowercase - converting string to lowercase");
+                set = set.toLowerCase();
+            }
+
             if (set.matches(FLAG_SET_REGEX)) {
                 cleanedUpSets.add(set);
             } else {
diff --git a/src/test/java/io/split/android/client/validators/FlagSetsValidatorImplTest.java b/src/test/java/io/split/android/client/validators/FlagSetsValidatorImplTest.java
index 5dce643d1..cd8bc9604 100644
--- a/src/test/java/io/split/android/client/validators/FlagSetsValidatorImplTest.java
+++ b/src/test/java/io/split/android/client/validators/FlagSetsValidatorImplTest.java
@@ -34,11 +34,12 @@ public void duplicatedInputValuesAreRemoved() {
 
     @Test
     public void valuesAreSortedAlphanumerically() {
-        List<String> result = mValidator.cleanup(Arrays.asList("set2", "set1", "set_1"));
-        assertEquals(3, result.size());
-        assertEquals("set1", result.get(0));
-        assertEquals("set2", result.get(1));
-        assertEquals("set_1", result.get(2));
+        List<String> result = mValidator.cleanup(Arrays.asList("set2", "set1", "set_1", "1set"));
+        assertEquals(4, result.size());
+        assertEquals("1set", result.get(0));
+        assertEquals("set1", result.get(1));
+        assertEquals("set2", result.get(2));
+        assertEquals("set_1", result.get(3));
     }
 
     @Test
@@ -75,10 +76,19 @@ public void nullSetIsRemoved() {
 
     @Test
     public void setWithExtraWhitespaceIsTrimmed() {
-        List<String> result = mValidator.cleanup(Arrays.asList("set1 ", " set2", "set3", "set 4"));
+        List<String> result = mValidator.cleanup(Arrays.asList("set1 ", " set2\r", "set3  ", "set 4\n"));
         assertEquals(3, result.size());
         assertEquals("set1", result.get(0));
         assertEquals("set2", result.get(1));
         assertEquals("set3", result.get(2));
     }
+
+    @Test
+    public void setsAreLowercase() {
+        List<String> result = mValidator.cleanup(Arrays.asList("SET1", "Set2", "SET_3"));
+        assertEquals(3, result.size());
+        assertEquals("set1", result.get(0));
+        assertEquals("set2", result.get(1));
+        assertEquals("set_3", result.get(2));
+    }
 }