diff --git a/src/apps/icon-o-matic/IconEditorApp.cpp b/src/apps/icon-o-matic/IconEditorApp.cpp
index 8375e00888..f0810e020f 100644
--- a/src/apps/icon-o-matic/IconEditorApp.cpp
+++ b/src/apps/icon-o-matic/IconEditorApp.cpp
@@ -740,7 +740,7 @@ IconEditorApp::_InstallDocumentMimeType()
 			strerror(ret));
 
 	// set sniffer rule
-	const char* snifferRule = "0.9 ('GSMI')";
+	const char* snifferRule = "0.9 ('IMSG')";
 	ret = mime.SetSnifferRule(snifferRule);
 	if (ret < B_OK) {
 		BString parseError;
diff --git a/src/apps/icon-o-matic/document/Defines.cpp b/src/apps/icon-o-matic/document/Defines.cpp
index f6df1a8e94..da93274a3f 100644
--- a/src/apps/icon-o-matic/document/Defines.cpp
+++ b/src/apps/icon-o-matic/document/Defines.cpp
@@ -7,7 +7,7 @@
  */
 #include "Defines.h"
 
-const uint32 kNativeIconMagicNumber = 'GSMI';
+const uint32 kNativeIconMagicNumber = 'IMSG';
 const char*	kNativeIconMimeType	= "application/x-vnd.Haiku-icon";
 
 
diff --git a/src/apps/icon-o-matic/import_export/message/MessageExporter.cpp b/src/apps/icon-o-matic/import_export/message/MessageExporter.cpp
index cd34ede0dc..f1a6b5cb37 100644
--- a/src/apps/icon-o-matic/import_export/message/MessageExporter.cpp
+++ b/src/apps/icon-o-matic/import_export/message/MessageExporter.cpp
@@ -104,7 +104,7 @@ MessageExporter::Export(const Icon* icon, BPositionIO* stream)
 	// later tells us that this file is one of us
 	if (ret == B_OK) {
 		ssize_t size = sizeof(uint32);
-		uint32 magic = B_HOST_TO_LENDIAN_INT32(kNativeIconMagicNumber);
+		uint32 magic = B_HOST_TO_BENDIAN_INT32(kNativeIconMagicNumber);
 		ssize_t written = stream->Write(&magic, size);
 		if (written != size) {
 			if (written < 0)
diff --git a/src/apps/icon-o-matic/import_export/message/MessageImporter.cpp b/src/apps/icon-o-matic/import_export/message/MessageImporter.cpp
index ede1dab285..6c3a5b544d 100644
--- a/src/apps/icon-o-matic/import_export/message/MessageImporter.cpp
+++ b/src/apps/icon-o-matic/import_export/message/MessageImporter.cpp
@@ -59,7 +59,7 @@ MessageImporter::Import(Icon* icon, BPositionIO* stream)
 		return ret;
 	}
 
-	if (B_LENDIAN_TO_HOST_INT32(magic) != kNativeIconMagicNumber) {
+	if (B_BENDIAN_TO_HOST_INT32(magic) != kNativeIconMagicNumber) {
 		// this might be an old native icon file, where
 		// we didn't prepend the magic number yet, seek back
 		if (stream->Seek(position, SEEK_SET) != position) {