diff --git a/reckon-core/src/main/java/org/ajoberstar/reckon/core/Reckoner.java b/reckon-core/src/main/java/org/ajoberstar/reckon/core/Reckoner.java
index 348dd1e9..129f34ab 100644
--- a/reckon-core/src/main/java/org/ajoberstar/reckon/core/Reckoner.java
+++ b/reckon-core/src/main/java/org/ajoberstar/reckon/core/Reckoner.java
@@ -100,6 +100,7 @@ private Version reckonTargetVersion(VcsInventory inventory, Version targetNormal
     String stage = stageCalc.apply(inventory, targetNormal)
         .map(String::trim)
         .filter(s -> !s.isEmpty())
+        .map(String::toLowerCase)
         .orElse(null);
 
     if (stage != null && !stages.contains(stage)) {
@@ -191,7 +192,9 @@ public Builder scopeCalc(Function<VcsInventory, Optional<String>> scopeCalc) {
      * @return this builder
      */
     public Builder stages(String... stages) {
-      this.stages = Arrays.stream(stages).collect(Collectors.toSet());
+      this.stages = Arrays.stream(stages)
+          .map(String::toLowerCase)
+          .collect(Collectors.toSet());
       this.defaultStage = this.stages.stream()
           .filter(name -> !FINAL_STAGE.equals(name))
           .sorted()
diff --git a/reckon-core/src/test/groovy/org/ajoberstar/reckon/core/ReckonerTest.groovy b/reckon-core/src/test/groovy/org/ajoberstar/reckon/core/ReckonerTest.groovy
index 1dc4e17d..20f4d8db 100644
--- a/reckon-core/src/test/groovy/org/ajoberstar/reckon/core/ReckonerTest.groovy
+++ b/reckon-core/src/test/groovy/org/ajoberstar/reckon/core/ReckonerTest.groovy
@@ -18,6 +18,34 @@ class ReckonerTest extends Specification {
     thrown(IllegalArgumentException)
   }
 
+  @Unroll
+  def 'stages are lowercased'(String stage) {
+    given:
+    VcsInventory inventory = new VcsInventory(
+      'abcdef',
+      true,
+      null,
+      Version.valueOf('1.2.3-beta.1'),
+      Version.valueOf('1.2.2'),
+      1,
+      [Version.valueOf('1.3.0')] as Set,
+      [Version.valueOf('2.0.0-rc.1')] as Set
+    )
+    when:
+    Reckoner.builder()
+      .clock(CLOCK)
+      .vcs { -> inventory }
+      .scopeCalc { i -> Optional.empty() }
+      .stages('beTA', 'miLEStone', 'RC', 'Final')
+      .stageCalc { i, v -> Optional.ofNullable(stage) }
+      .build()
+      .reckon()
+    then:
+    notThrown(IllegalArgumentException)
+    where:
+    stage << ['BeTa', 'Milestone', 'rc', 'fINal']
+  }
+
   def 'if version is claimed, throw'() {
     given:
     VcsInventory inventory = new VcsInventory(