diff --git a/Makefile.am b/Makefile.am
index b11af04ad..bb681876d 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -742,7 +742,7 @@ EXTRA_DIST = \
   src/res/mouse.bmp \
   src/res/Rectangle.bmp \
   src/res/ocd.ico \
-  src/res/c4m.ico \
+  src/res/ocm.ico \
   src/res/c4x.xpm \
   src/res/fill1.bmp \
   src/res/ift1.bmp \
diff --git a/planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Ice.c4m b/planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Ice.ocm
similarity index 100%
rename from planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Ice.c4m
rename to planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Ice.ocm
diff --git a/planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Snow.c4m b/planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Snow.ocm
similarity index 100%
rename from planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Snow.c4m
rename to planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Snow.ocm
diff --git a/planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Water.c4m b/planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Water.ocm
similarity index 100%
rename from planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Water.c4m
rename to planet/BackToTheRocks.ocf/FrozenFortress.ocs/Material.ocg/Water.ocm
diff --git a/planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ametyst.c4m b/planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ametyst.ocm
similarity index 100%
rename from planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ametyst.c4m
rename to planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ametyst.ocm
diff --git a/planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ruby.c4m b/planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ruby.ocm
similarity index 100%
rename from planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ruby.c4m
rename to planet/BackToTheRocks.ocf/Hideout.ocs/Material.ocg/Ruby.ocm
diff --git a/planet/Material.ocg/Acid.c4m b/planet/Material.ocg/Acid.ocm
similarity index 100%
rename from planet/Material.ocg/Acid.c4m
rename to planet/Material.ocg/Acid.ocm
diff --git a/planet/Material.ocg/Brick.c4m b/planet/Material.ocg/Brick.ocm
similarity index 100%
rename from planet/Material.ocg/Brick.c4m
rename to planet/Material.ocg/Brick.ocm
diff --git a/planet/Material.ocg/BrickSoft.c4m b/planet/Material.ocg/BrickSoft.ocm
similarity index 100%
rename from planet/Material.ocg/BrickSoft.c4m
rename to planet/Material.ocg/BrickSoft.ocm
diff --git a/planet/Material.ocg/Coal.c4m b/planet/Material.ocg/Coal.ocm
similarity index 100%
rename from planet/Material.ocg/Coal.c4m
rename to planet/Material.ocg/Coal.ocm
diff --git a/planet/Material.ocg/DuroLava.c4m b/planet/Material.ocg/DuroLava.ocm
similarity index 100%
rename from planet/Material.ocg/DuroLava.c4m
rename to planet/Material.ocg/DuroLava.ocm
diff --git a/planet/Material.ocg/Earth.c4m b/planet/Material.ocg/Earth.ocm
similarity index 100%
rename from planet/Material.ocg/Earth.c4m
rename to planet/Material.ocg/Earth.ocm
diff --git a/planet/Material.ocg/Gold.c4m b/planet/Material.ocg/Gold.ocm
similarity index 100%
rename from planet/Material.ocg/Gold.c4m
rename to planet/Material.ocg/Gold.ocm
diff --git a/planet/Material.ocg/Granite.c4m b/planet/Material.ocg/Granite.ocm
similarity index 100%
rename from planet/Material.ocg/Granite.c4m
rename to planet/Material.ocg/Granite.ocm
diff --git a/planet/Material.ocg/Ice.c4m b/planet/Material.ocg/Ice.ocm
similarity index 100%
rename from planet/Material.ocg/Ice.c4m
rename to planet/Material.ocg/Ice.ocm
diff --git a/planet/Material.ocg/Lava.c4m b/planet/Material.ocg/Lava.ocm
similarity index 100%
rename from planet/Material.ocg/Lava.c4m
rename to planet/Material.ocg/Lava.ocm
diff --git a/planet/Material.ocg/ORE.c4m b/planet/Material.ocg/ORE.ocm
similarity index 100%
rename from planet/Material.ocg/ORE.c4m
rename to planet/Material.ocg/ORE.ocm
diff --git a/planet/Material.ocg/Rock.c4m b/planet/Material.ocg/Rock.ocm
similarity index 100%
rename from planet/Material.ocg/Rock.c4m
rename to planet/Material.ocg/Rock.ocm
diff --git a/planet/Material.ocg/Sand.c4m b/planet/Material.ocg/Sand.ocm
similarity index 100%
rename from planet/Material.ocg/Sand.c4m
rename to planet/Material.ocg/Sand.ocm
diff --git a/planet/Material.ocg/SandDry.c4m b/planet/Material.ocg/SandDry.ocm
similarity index 100%
rename from planet/Material.ocg/SandDry.c4m
rename to planet/Material.ocg/SandDry.ocm
diff --git a/planet/Material.ocg/Snow.c4m b/planet/Material.ocg/Snow.ocm
similarity index 100%
rename from planet/Material.ocg/Snow.c4m
rename to planet/Material.ocg/Snow.ocm
diff --git a/planet/Material.ocg/Sulphur.c4m b/planet/Material.ocg/Sulphur.ocm
similarity index 100%
rename from planet/Material.ocg/Sulphur.c4m
rename to planet/Material.ocg/Sulphur.ocm
diff --git a/planet/Material.ocg/Tunnel.c4m b/planet/Material.ocg/Tunnel.ocm
similarity index 100%
rename from planet/Material.ocg/Tunnel.c4m
rename to planet/Material.ocg/Tunnel.ocm
diff --git a/planet/Material.ocg/Vehicle.c4m b/planet/Material.ocg/Vehicle.ocm
similarity index 100%
rename from planet/Material.ocg/Vehicle.c4m
rename to planet/Material.ocg/Vehicle.ocm
diff --git a/planet/Material.ocg/Water.c4m b/planet/Material.ocg/Water.ocm
similarity index 100%
rename from planet/Material.ocg/Water.c4m
rename to planet/Material.ocg/Water.ocm
diff --git a/src/c4group/C4Components.h b/src/c4group/C4Components.h
index 47a1ce4cb..3e69b94af 100644
--- a/src/c4group/C4Components.h
+++ b/src/c4group/C4Components.h
@@ -146,7 +146,7 @@
 
 #define C4CFN_DefFiles        "*.ocd"
 #define C4CFN_PlayerFiles     "*.ocp"
-#define C4CFN_MaterialFiles   "*.c4m"
+#define C4CFN_MaterialFiles   "*.ocm"
 #define C4CFN_ObjectInfoFiles "*.oci"
 #define C4CFN_MusicFiles      "*.mid"
 #define C4CFN_SoundFiles      "*.wav|*.ogg"
@@ -173,7 +173,7 @@
 #define C4FLS_Player    "Player.txt|Portrait.png|Portrait.bmp|*.oci"
 #define C4FLS_Object    "ObjectInfo.txt|Portrait.png|Portrait.bmp"
 #define C4FLS_Folder    "Folder.txt|Title*.txt|Info.txt|Desc*.rtf|Title.png|Title.bmp|Icon.png|Icon.bmp|Author.txt|Version.txt|*.ocs|Loader*.bmp|Loader*.png|Loader*.jpeg|Loader*.jpg|FolderMap.txt|FolderMap.png"
-#define C4FLS_Material  "TexMap.txt|*.bmp|*.png|*.c4m"
+#define C4FLS_Material  "TexMap.txt|*.bmp|*.png|*.ocm"
 #define C4FLS_Graphics  "Loader*.bmp|Loader*.png|Loader*.jpeg|Loader*.jpg|FontEndeavour12.png|FontEndeavour24.png|FontEndeavour16.png|FontEndeavour10.png|Font*.png"\
             "|*.pal|Control.png|Fire.png|Background.png|Flag.png|Crew.png|Wealth.png|Player.png|Rank.png|Entry.png|Captain.png|Cursor.png|CursorSmall.png|CursorMedium.png|CursorLarge.png|SelectMark.png|MenuSymbol.png|Menu.png|Logo.png|Construction.png|Energy.png|Options.png|UpperBoard.png|Arrow.png|Exit.png|Hand.png|Gamepad.png|Build.png|Liquid.png"\
             "|GUICaption.png|GUIButton.png|GUIButtonDown.png|GUIButtonHighlight.png|GUIIcons.png|GUIIcons2.png|GUIScroll.png|GUIContext.png|GUISubmenu.png|GUICheckBox.png|GUIBigArrows.png|GUIProgress.png"\
diff --git a/src/platform/C4FileClasses.cpp b/src/platform/C4FileClasses.cpp
index 4d3c62dae..a7104849b 100644
--- a/src/platform/C4FileClasses.cpp
+++ b/src/platform/C4FileClasses.cpp
@@ -54,7 +54,7 @@ bool SetC4FileClasses(const char *szEnginePath)
 	if (!SetRegFileClass("OpenClonk.Player",     ,"ocp", "OpenClonk Player",            szEnginePath, 4, C4FileClassContentType)) return false;
 	if (!SetRegFileClass("OpenClonk.Definition", ,"ocd", "OpenClonk Object Definition", szEnginePath, 5, C4FileClassContentType)) return false;
 	if (!SetRegFileClass("OpenClonk.Object",     ,"oci", "OpenClonk Object Info",       szEnginePath, 6, C4FileClassContentType)) return false;
-	if (!SetRegFileClass("Clonk4.Material",   "c4m", "Clonk 4 Material",          szEnginePath, 7, "text/plain")) return false;
+	if (!SetRegFileClass("OpenClonk.Material",   ,"ocm", "OpenClonk Material",          szEnginePath, 7, "text/plain")) return false;
 	if (!SetRegFileClass("Clonk4.Binary",     "c4b", "Clonk 4 Binary",            szEnginePath, 8, "application/octet-stream")) return false;
 	if (!SetRegFileClass("Clonk4.Video",      "c4v", "Clonk 4 Video",             szEnginePath, 9, "video/avi")) return false;
 	if (!SetRegFileClass("Clonk4.Weblink",    "c4l", "Clonk 4 Weblink",           szEnginePath, 10, C4FileClassContentType)) return false;
diff --git a/src/res/c4m.ico b/src/res/c4m.ico
deleted file mode 100644
index b36b90e1b..000000000
Binary files a/src/res/c4m.ico and /dev/null differ
diff --git a/src/res/engine.rc b/src/res/engine.rc
index dd7aa97db..17a2d621b 100644
--- a/src/res/engine.rc
+++ b/src/res/engine.rc
@@ -38,7 +38,7 @@ IDI_03_OCF              ICON    DISCARDABLE     "ocf.ico"
 IDI_04_OCP              ICON    DISCARDABLE     "ocp.ico"
 IDI_06_OCD              ICON    DISCARDABLE     "ocd.ico"
 IDI_07_OCI              ICON    DISCARDABLE     "oci.ico"
-IDI_08_C4M              ICON    DISCARDABLE     "c4m.ico"
+IDI_08_OCM              ICON    DISCARDABLE     "ocm.ico"
 IDI_09_C4B              ICON    DISCARDABLE     "c4b.ico"
 IDI_10_C4V              ICON    DISCARDABLE     "c4v.ico"
 IDI_11_C4L              ICON    DISCARDABLE     "c4l.ico"
diff --git a/src/res/ocm.ico b/src/res/ocm.ico
new file mode 100644
index 000000000..1487629a4
Binary files /dev/null and b/src/res/ocm.ico differ
diff --git a/src/res/resource.h b/src/res/resource.h
index 71410a0bd..f46db16f8 100644
--- a/src/res/resource.h
+++ b/src/res/resource.h
@@ -65,7 +65,7 @@
 #define IDI_04_OCP                      4004
 #define IDI_06_OCD                      4006
 #define IDI_07_OCI                      4007
-#define IDI_08_C4M                      4008
+#define IDI_08_OCM                      4008
 #define IDI_09_C4B                      4009
 #define IDI_10_C4V                      4010
 #define IDI_11_C4L                      4011
diff --git a/tools/install/oc.nsi b/tools/install/oc.nsi
index ed04ad47e..7f85cc867 100644
--- a/tools/install/oc.nsi
+++ b/tools/install/oc.nsi
@@ -115,8 +115,8 @@ Section -Post
   WriteRegStr HKCR ".ocd\Content Type" "" "vnd.clonk.c4group"
   WriteRegStr HKCR ".oci" "" "OpenClonk.Object"
   WriteRegStr HKCR ".oci\Content Type" "" "vnd.clonk.c4group"
-  WriteRegStr HKCR ".c4m" "" "Clonk4.Material"
-  WriteRegStr HKCR ".c4m\Content Type" "" "text/plain"
+  WriteRegStr HKCR ".ocm" "" "OpenClonk.Material"
+  WriteRegStr HKCR ".ocm\Content Type" "" "text/plain"
   WriteRegStr HKCR ".c4b" "" "Clonk4.Binary"
   WriteRegStr HKCR ".c4b\Content Type" "" "application/octet-stream"
   WriteRegStr HKCR ".c4v" "" "Clonk4.Video"
@@ -138,8 +138,8 @@ Section -Post
   WriteRegStr HKCR "OpenClonk.Definition\DefaultIcon" "" "$INSTDIR\Clonk.exe,5"
   WriteRegStr HKCR "OpenClonk.Object" "" "OpenClonk Object Info"
   WriteRegStr HKCR "OpenClonk.Object\DefaultIcon" "" "$INSTDIR\Clonk.exe,6"
-  WriteRegStr HKCR "Clonk4.Material" "" "Clonk 4 Material"
-  WriteRegStr HKCR "Clonk4.Material\DefaultIcon" "" "$INSTDIR\Clonk.exe,7"
+  WriteRegStr HKCR "OpenClonk.Material" "" "OpenClonk Material"
+  WriteRegStr HKCR "OpenClonk.Material\DefaultIcon" "" "$INSTDIR\Clonk.exe,7"
   WriteRegStr HKCR "Clonk4.Binary" "" "Clonk 4 Binary"
   WriteRegStr HKCR "Clonk4.Binary\DefaultIcon" "" "$INSTDIR\Clonk.exe,8"
   WriteRegStr HKCR "Clonk4.Video" "" "Clonk 4 Video"
@@ -207,8 +207,8 @@ Section Uninstall
   DeleteRegKey HKCR "OpenClonk.Definition"
   DeleteRegKey HKCR ".oci"
   DeleteRegKey HKCR "OpenClonk.Object"
-  DeleteRegKey HKCR ".c4m"
-  DeleteRegKey HKCR "Clonk4.Material"
+  DeleteRegKey HKCR ".ocm"
+  DeleteRegKey HKCR "OpenClonk.Material"
   DeleteRegKey HKCR ".c4b"
   DeleteRegKey HKCR "Clonk4.Binary"
   DeleteRegKey HKCR ".c4v"