diff --git a/Octokit/Http/ApiInfoParser.cs b/Octokit/Http/ApiInfoParser.cs
index 94a51c5649..2d7bf20f8f 100644
--- a/Octokit/Http/ApiInfoParser.cs
+++ b/Octokit/Http/ApiInfoParser.cs
@@ -16,6 +16,11 @@ internal static class ApiInfoParser
         static readonly Regex _linkRelRegex = new Regex("rel=\"(next|prev|first|last)\"", regexOptions);
         static readonly Regex _linkUriRegex = new Regex("<(.+)>", regexOptions);
 
+        static KeyValuePair<string, string> LookupHeader(IDictionary<string, string> headers, string key)
+        {
+            return headers.FirstOrDefault(h => string.Equals(h.Key, key, StringComparison.OrdinalIgnoreCase));
+        }
+
         public static ApiInfo ParseResponseHeaders(IDictionary<string, string> responseHeaders)
         {
             Ensure.ArgumentNotNull(responseHeaders, nameof(responseHeaders));
@@ -25,28 +30,32 @@ public static ApiInfo ParseResponseHeaders(IDictionary<string, string> responseH
             var acceptedOauthScopes = new List<string>();
             string etag = null;
 
-            if (responseHeaders.ContainsKey("X-Accepted-OAuth-Scopes"))
+            var acceptedOauthScopesKey = LookupHeader(responseHeaders, "X-Accepted-OAuth-Scopes");
+            if (!acceptedOauthScopesKey.Equals(default(KeyValuePair<string, string>)))
             {
-                acceptedOauthScopes.AddRange(responseHeaders["X-Accepted-OAuth-Scopes"]
+                acceptedOauthScopes.AddRange(acceptedOauthScopesKey.Value
                     .Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
                     .Select(x => x.Trim()));
             }
 
-            if (responseHeaders.ContainsKey("X-OAuth-Scopes"))
+            var oauthScopesKey = LookupHeader(responseHeaders, "X-OAuth-Scopes");
+            if (!oauthScopesKey.Equals(default(KeyValuePair<string, string>)))
             {
-                oauthScopes.AddRange(responseHeaders["X-OAuth-Scopes"]
+                oauthScopes.AddRange(oauthScopesKey.Value
                     .Split(new[] { ',' }, StringSplitOptions.RemoveEmptyEntries)
                     .Select(x => x.Trim()));
             }
 
-            if (responseHeaders.ContainsKey("ETag"))
+            var etagKey = LookupHeader(responseHeaders, "ETag");
+            if (!etagKey.Equals(default(KeyValuePair<string, string>)))
             {
-                etag = responseHeaders["ETag"];
+                etag = etagKey.Value;
             }
 
-            if (responseHeaders.ContainsKey("Link"))
+            var linkKey = LookupHeader(responseHeaders, "Link");
+            if (!linkKey.Equals(default(KeyValuePair<string, string>)))
             {
-                var links = responseHeaders["Link"].Split(',');
+                var links = linkKey.Value.Split(',');
                 foreach (var link in links)
                 {
                     var relMatch = _linkRelRegex.Match(link);
diff --git a/Octokit/Http/RateLimit.cs b/Octokit/Http/RateLimit.cs
index a5c2f28800..a3d434cf51 100644
--- a/Octokit/Http/RateLimit.cs
+++ b/Octokit/Http/RateLimit.cs
@@ -3,6 +3,7 @@
 using System.Diagnostics;
 using System.Diagnostics.CodeAnalysis;
 using System.Globalization;
+using System.Linq;
 #if !NO_SERIALIZABLE
 using System.Runtime.Serialization;
 #endif
@@ -65,11 +66,27 @@ public RateLimit(int limit, int remaining, long resetAsUtcEpochSeconds)
         [Parameter(Key = "reset")]
         public long ResetAsUtcEpochSeconds { get; private set; }
 
+        static KeyValuePair<string, string> LookupHeader(IDictionary<string, string> headers, string key)
+        {
+            return headers.FirstOrDefault(h => string.Equals(h.Key, key, StringComparison.OrdinalIgnoreCase));
+        }
+
         static long GetHeaderValueAsInt32Safe(IDictionary<string, string> responseHeaders, string key)
         {
-            string value;
             long result;
-            return !responseHeaders.TryGetValue(key, out value) || value == null || !long.TryParse(value, out result)
+
+            var foundKey = LookupHeader(responseHeaders, key);
+            if (foundKey.Equals(default(KeyValuePair<string, string>)))
+            {
+                return 0;
+            }
+
+            if (string.IsNullOrWhiteSpace(foundKey.Value))
+            {
+                return 0;
+            }
+
+            return !long.TryParse(foundKey.Value, out result)
                 ? 0
                 : result;
         }