diff --git a/dom/security/nsContentSecurityManager.cpp b/dom/security/nsContentSecurityManager.cpp
index f689286d6be5..b92818201e76 100644
--- a/dom/security/nsContentSecurityManager.cpp
+++ b/dom/security/nsContentSecurityManager.cpp
@@ -112,7 +112,7 @@ bool nsContentSecurityManager::AllowTopLevelNavigationToDataURI(
 
   // Allow data: images as long as they are not SVGs
   if (StringBeginsWith(contentType, "image/"_ns) &&
-      !contentType.EqualsLiteral("image/svg+xml")) {
+      !contentType.EqualsLiteral(IMAGE_SVG_XML)) {
     return true;
   }
   // Allow all data: PDFs. or JSON documents
diff --git a/dom/serializers/nsDocumentEncoder.cpp b/dom/serializers/nsDocumentEncoder.cpp
index ea5c6de77e58..c10594820f04 100644
--- a/dom/serializers/nsDocumentEncoder.cpp
+++ b/dom/serializers/nsDocumentEncoder.cpp
@@ -31,6 +31,7 @@
 #include "mozilla/dom/Selection.h"
 #include "nsContentUtils.h"
 #include "nsElementTable.h"
+#include "nsMimeTypes.h"
 #include "nsUnicharUtils.h"
 #include "nsReadableUtils.h"
 #include "nsTArray.h"
@@ -1534,12 +1535,12 @@ nsDocumentEncoder::SetNodeFixup(nsIDocumentEncoderNodeFixup* aFixup) {
 }
 
 bool do_getDocumentTypeSupportedForEncoding(const char* aContentType) {
-  if (!nsCRT::strcmp(aContentType, "text/xml") ||
-      !nsCRT::strcmp(aContentType, "application/xml") ||
-      !nsCRT::strcmp(aContentType, "application/xhtml+xml") ||
-      !nsCRT::strcmp(aContentType, "image/svg+xml") ||
-      !nsCRT::strcmp(aContentType, "text/html") ||
-      !nsCRT::strcmp(aContentType, "text/plain")) {
+  if (!nsCRT::strcmp(aContentType, TEXT_XML) ||
+      !nsCRT::strcmp(aContentType, APPLICATION_XML) ||
+      !nsCRT::strcmp(aContentType, APPLICATION_XHTML_XML) ||
+      !nsCRT::strcmp(aContentType, IMAGE_SVG_XML) ||
+      !nsCRT::strcmp(aContentType, TEXT_HTML) ||
+      !nsCRT::strcmp(aContentType, TEXT_PLAIN)) {
     return true;
   }
   return false;
diff --git a/gfx/thebes/gfxSVGGlyphs.cpp b/gfx/thebes/gfxSVGGlyphs.cpp
index a668f9070337..d1297a33fb50 100644
--- a/gfx/thebes/gfxSVGGlyphs.cpp
+++ b/gfx/thebes/gfxSVGGlyphs.cpp
@@ -129,7 +129,7 @@ gfxSVGGlyphsDocument* gfxSVGGlyphs::FindOrCreateGlyphsDocument(
 
 nsresult gfxSVGGlyphsDocument::SetupPresentation() {
   nsCOMPtr<nsIDocumentLoaderFactory> docLoaderFactory =
-      nsContentUtils::FindInternalDocumentViewer("image/svg+xml"_ns);
+      nsContentUtils::FindInternalDocumentViewer(SVG_CONTENT_TYPE);
   NS_ASSERTION(docLoaderFactory, "Couldn't get DocumentLoaderFactory");
 
   nsCOMPtr<nsIDocumentViewer> viewer;
diff --git a/image/imgLoader.cpp b/image/imgLoader.cpp
index dc6f412542a2..e94cf0836896 100644
--- a/image/imgLoader.cpp
+++ b/image/imgLoader.cpp
@@ -2845,7 +2845,7 @@ bool imgLoader::SupportImageWithMimeType(const nsACString& aMimeType,
   ToLowerCase(mimeType);
 
   if (aAccept == AcceptedMimeTypes::IMAGES_AND_DOCUMENTS &&
-      mimeType.EqualsLiteral("image/svg+xml")) {
+      mimeType.EqualsLiteral(IMAGE_SVG_XML)) {
     return true;
   }
 
diff --git a/widget/nsITransferable.idl b/widget/nsITransferable.idl
index c6e424d7cb41..9f4df85e6266 100644
--- a/widget/nsITransferable.idl
+++ b/widget/nsITransferable.idl
@@ -31,6 +31,7 @@ interface nsIReferrerInfo;
 #define kJPEGImageMime              "image/jpeg"
 #define kJPGImageMime               "image/jpg"
 #define kGIFImageMime               "image/gif"
+#define kSVGImageMime               "image/svg+xml"
 #define kFileMime                   "application/x-moz-file"
 
 #define kURLMime                    "text/x-moz-url"        // data contains url\ntitle