diff --git a/src/ajax.js b/src/ajax.js
index ca2b910dd..27abe375e 100644
--- a/src/ajax.js
+++ b/src/ajax.js
@@ -406,6 +406,9 @@ jQuery.extend( {
 			// Url cleanup var
 			urlAnchor,
 
+			// Request state (becomes false upon send and true upon completion)
+			completed,
+
 			// To know if global events are to be dispatched
 			fireGlobals,
 
@@ -435,9 +438,6 @@ jQuery.extend( {
 			requestHeaders = {},
 			requestHeadersNames = {},
 
-			// The jqXHR state
-			state = 0,
-
 			// Default abort message
 			strAbort = "canceled",
 
@@ -448,7 +448,7 @@ jQuery.extend( {
 				// Builds headers hashtable if needed
 				getResponseHeader: function( key ) {
 					var match;
-					if ( state === 2 ) {
+					if ( completed ) {
 						if ( !responseHeaders ) {
 							responseHeaders = {};
 							while ( ( match = rheaders.exec( responseHeadersString ) ) ) {
@@ -462,14 +462,14 @@ jQuery.extend( {
 
 				// Raw string
 				getAllResponseHeaders: function() {
-					return state === 2 ? responseHeadersString : null;
+					return completed ? responseHeadersString : null;
 				},
 
 				// Caches the header
 				setRequestHeader: function( name, value ) {
-					var lname = name.toLowerCase();
-					if ( !state ) {
-						name = requestHeadersNames[ lname ] = requestHeadersNames[ lname ] || name;
+					if ( completed == null ) {
+						name = requestHeadersNames[ name.toLowerCase() ] =
+							requestHeadersNames[ name.toLowerCase() ] || name;
 						requestHeaders[ name ] = value;
 					}
 					return this;
@@ -477,7 +477,7 @@ jQuery.extend( {
 
 				// Overrides response content-type header
 				overrideMimeType: function( type ) {
-					if ( !state ) {
+					if ( completed == null ) {
 						s.mimeType = type;
 					}
 					return this;
@@ -487,16 +487,16 @@ jQuery.extend( {
 				statusCode: function( map ) {
 					var code;
 					if ( map ) {
-						if ( state < 2 ) {
-							for ( code in map ) {
-
-								// Lazy-add the new callback in a way that preserves old ones
-								statusCode[ code ] = [ statusCode[ code ], map[ code ] ];
-							}
-						} else {
+						if ( completed ) {
 
 							// Execute the appropriate callbacks
 							jqXHR.always( map[ jqXHR.status ] );
+						} else {
+
+							// Lazy-add the new callbacks in a way that preserves old ones
+							for ( code in map ) {
+								statusCode[ code ] = [ statusCode[ code ], map[ code ] ];
+							}
 						}
 					}
 					return this;
@@ -560,7 +560,7 @@ jQuery.extend( {
 		inspectPrefiltersOrTransports( prefilters, s, options, jqXHR );
 
 		// If request was aborted inside a prefilter, stop there
-		if ( state === 2 ) {
+		if ( completed ) {
 			return jqXHR;
 		}
 
@@ -642,7 +642,7 @@ jQuery.extend( {
 
 		// Allow custom headers/mimetypes and early abort
 		if ( s.beforeSend &&
-			( s.beforeSend.call( callbackContext, jqXHR, s ) === false || state === 2 ) ) {
+			( s.beforeSend.call( callbackContext, jqXHR, s ) === false || completed ) ) {
 
 			// Abort if not done already and return
 			return jqXHR.abort();
@@ -671,7 +671,7 @@ jQuery.extend( {
 			}
 
 			// If request was aborted inside ajaxSend, stop there
-			if ( state === 2 ) {
+			if ( completed ) {
 				return jqXHR;
 			}
 
@@ -683,18 +683,17 @@ jQuery.extend( {
 			}
 
 			try {
-				state = 1;
+				completed = false;
 				transport.send( requestHeaders, done );
 			} catch ( e ) {
 
-				// Propagate exception as error if not done
-				if ( state < 2 ) {
-					done( -1, e );
-
-				// Simply rethrow otherwise
-				} else {
+				// Rethrow post-completion exceptions
+				if ( completed ) {
 					throw e;
 				}
+
+				// Propagate others as results
+				done( -1, e );
 			}
 		}
 
@@ -703,13 +702,12 @@ jQuery.extend( {
 			var isSuccess, success, error, response, modified,
 				statusText = nativeStatusText;
 
-			// Called once
-			if ( state === 2 ) {
+			// Ignore repeat invocations
+			if ( completed ) {
 				return;
 			}
 
-			// State is "done" now
-			state = 2;
+			completed = true;
 
 			// Clear timeout if it exists
 			if ( timeoutTimer ) {