diff --git a/Classes/Core/OMDeferred.h b/Classes/Core/OMDeferred.h
index 22a1687..718a754 100644
--- a/Classes/Core/OMDeferred.h
+++ b/Classes/Core/OMDeferred.h
@@ -2,7 +2,7 @@
 // OMPromise.h
 // OMPromises
 //
-// Copyright (C) 2013,2014 Oliver Mader
+// Copyright (C) 2013-2015 Oliver Mader
 // 
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -76,7 +76,7 @@
 
 /** Finalizes the deferred by settings its state to OMPromiseStateFulfilled.
  
- Implicitly sets the progress to 1.
+ Implicitly sets the progress to 1.0f.
  
  @param result Result to set and propagate.
  @see fail:
@@ -93,7 +93,7 @@
 /** Update the progress.
  
  The new progress has to be higher than the previous one. Equal values are skipped,
- but lower values raise an exception.
+ but lower values raise an exception. The progress must be less than or equal to 1.0f.
  
  @param progress Higher progress to set and propagate.
  */
diff --git a/Classes/Core/OMDeferred.m b/Classes/Core/OMDeferred.m
index 4aee602..02dd5d6 100644
--- a/Classes/Core/OMDeferred.m
+++ b/Classes/Core/OMDeferred.m
@@ -2,7 +2,7 @@
 // OMPromise.h
 // OMPromises
 //
-// Copyright (C) 2013,2014 Oliver Mader
+// Copyright (C) 2013-2015 Oliver Mader
 // 
 // Permission is hereby granted, free of charge, to any person obtaining a copy
 // of this software and associated documentation files (the "Software"), to deal
@@ -88,9 +88,10 @@ - (void)progress:(float)progress {
     @synchronized (self) {
         NSAssert(self.state == OMPromiseStateUnfulfilled, @"Can only progress while being Unfulfilled");
         NSAssert(self.progress <= progress + FLT_EPSILON, @"Progress must not decrease");
+        NSAssert(progress <= 1.0f + FLT_EPSILON, @"Progress must be in range (0, 1]");
         
         if (self.progress < progress - FLT_EPSILON) {
-            self.progress = progress;
+            self.progress = MIN(1.0f, progress);
             progressHandlers = self.progressHandlers;
         }
         
diff --git a/Classes/HTTP/OMHTTPRequest.m b/Classes/HTTP/OMHTTPRequest.m
index a88e79a..f6be9cc 100644
--- a/Classes/HTTP/OMHTTPRequest.m
+++ b/Classes/HTTP/OMHTTPRequest.m
@@ -103,8 +103,8 @@ - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
     [self.data appendData:data];
     
     if (self.expectedContentLength > 0) {
-        [self progress:self.lookup + (1 - self.lookup) *
-                (float)self.data.length / self.expectedContentLength];
+        [self progress:MIN(1.0f, self.lookup + (1 - self.lookup) *
+                (float)self.data.length / self.expectedContentLength)];
     }
 }
 
diff --git a/Tests/Core/OMDeferredTests.m b/Tests/Core/OMDeferredTests.m
index 6e3241d..9dee054 100644
--- a/Tests/Core/OMDeferredTests.m
+++ b/Tests/Core/OMDeferredTests.m
@@ -90,6 +90,8 @@ - (void)testProgress {
     
     XCTAssertThrows([deferred progress:.1f], @"Must not decrease progress");
     XCTAssertEqualWithAccuracy(deferred.progress, .2f, FLT_EPSILON, @"Progress shouldn't have changed");
+    
+    XCTAssertThrows([deferred progress:1.1f], @"Progress must not exceed 1.0f");
 }
 
 - (void)testProgressPrecision {
@@ -97,7 +99,7 @@ - (void)testProgressPrecision {
     
     __block int called = 0;
     [deferred.promise progressed:^(float progress) {
-        float values[] = {.1f, .1 + 2.f*FLT_EPSILON};
+        float values[] = {.1f, .1 + 2.f*FLT_EPSILON, 1.0f};
         XCTAssertEqualWithAccuracy(values[called], progress, FLT_EPSILON, @"Unexpected progress");
         called += 1;
     }];
@@ -113,6 +115,9 @@ - (void)testProgressPrecision {
     
     [deferred progress:.1f + 2.f*FLT_EPSILON];
     XCTAssertEqual(called, 2, @"Finally we progress if the change is large enough");
+    
+    [deferred progress:1.0f + FLT_EPSILON];
+    XCTAssertEqual(deferred.progress, 1.0f);
 }
 
 - (void)testTryFulfil {