diff --git a/Classes/ASIDownloadCache.m b/Classes/ASIDownloadCache.m
index b0c99909..8cb1e04a 100644
--- a/Classes/ASIDownloadCache.m
+++ b/Classes/ASIDownloadCache.m
@@ -435,15 +435,19 @@ + (BOOL)serverAllowsResponseCachingForRequest:(ASIHTTPRequest *)request
 	return YES;
 }
 
-
-// Borrowed from: http://stackoverflow.com/questions/652300/using-md5-hash-on-a-string-in-cocoa
 + (NSString *)keyForURL:(NSURL *)url
 {
 	NSString *urlString = [url absoluteString];
+	if ([urlString length] == 0) {
+		return nil;
+	}
+
 	// Strip trailing slashes so http://allseeing-i.com/ASIHTTPRequest/ is cached the same as http://allseeing-i.com/ASIHTTPRequest
 	if ([[urlString substringFromIndex:[urlString length]-1] isEqualToString:@"/"]) {
 		urlString = [urlString substringToIndex:[urlString length]-1];
 	}
+
+	// Borrowed from: http://stackoverflow.com/questions/652300/using-md5-hash-on-a-string-in-cocoa
 	const char *cStr = [urlString UTF8String];
 	unsigned char result[16];
 	CC_MD5(cStr, (CC_LONG)strlen(cStr), result);
diff --git a/Classes/ASIHTTPRequest.m b/Classes/ASIHTTPRequest.m
index 369d4b11..34fa93e8 100644
--- a/Classes/ASIHTTPRequest.m
+++ b/Classes/ASIHTTPRequest.m
@@ -24,7 +24,7 @@
 #import "ASIDataCompressor.h"
 
 // Automatically set on build
-NSString *ASIHTTPRequestVersion = @"v1.8.1-2 2011-06-04";
+NSString *ASIHTTPRequestVersion = @"v1.8.1-4 2011-06-04";
 
 static NSString *defaultUserAgent = nil;