diff --git a/dlls/wined3d/shader.c b/dlls/wined3d/shader.c
index e5b969c572..feaa6b9875 100644
--- a/dlls/wined3d/shader.c
+++ b/dlls/wined3d/shader.c
@@ -1935,6 +1935,10 @@ static void shader_dump_register(struct wined3d_string_buffer *buffer,
             shader_addline(buffer, "vCoverage");
             break;
 
+        case WINED3DSPR_SAMPLEMASK:
+            shader_addline(buffer, "oMask");
+            break;
+
         default:
             shader_addline(buffer, "<unhandled_rtype(%#x)>", reg->type);
             break;
diff --git a/dlls/wined3d/shader_sm4.c b/dlls/wined3d/shader_sm4.c
index 4ed2391e8b..aa6aead727 100644
--- a/dlls/wined3d/shader_sm4.c
+++ b/dlls/wined3d/shader_sm4.c
@@ -292,6 +292,7 @@ enum wined3d_sm4_register_type
     WINED3D_SM4_RT_PRIMID                  = 0x0b,
     WINED3D_SM4_RT_DEPTHOUT                = 0x0c,
     WINED3D_SM4_RT_NULL                    = 0x0d,
+    WINED3D_SM4_RT_OMASK                   = 0x0f,
     WINED3D_SM5_RT_STREAM                  = 0x10,
     WINED3D_SM5_RT_FUNCTION_BODY           = 0x11,
     WINED3D_SM5_RT_FUNCTION_POINTER        = 0x13,
@@ -1001,7 +1002,7 @@ static const enum wined3d_shader_register_type register_type_table[] =
     /* WINED3D_SM4_RT_DEPTHOUT */                WINED3DSPR_DEPTHOUT,
     /* WINED3D_SM4_RT_NULL */                    WINED3DSPR_NULL,
     /* UNKNOWN */                                ~0u,
-    /* UNKNOWN */                                ~0u,
+    /* WINED3D_SM4_RT_OMASK */                   WINED3DSPR_SAMPLEMASK,
     /* WINED3D_SM5_RT_STREAM */                  WINED3DSPR_STREAM,
     /* WINED3D_SM5_RT_FUNCTION_BODY */           WINED3DSPR_FUNCTIONBODY,
     /* UNKNOWN */                                ~0u,
diff --git a/dlls/wined3d/wined3d_private.h b/dlls/wined3d/wined3d_private.h
index 0be5856c9c..d632d423b3 100644
--- a/dlls/wined3d/wined3d_private.h
+++ b/dlls/wined3d/wined3d_private.h
@@ -395,6 +395,7 @@ enum wined3d_shader_register_type
     WINED3DSPR_FUNCTIONBODY,
     WINED3DSPR_FUNCTIONPOINTER,
     WINED3DSPR_COVERAGE,
+    WINED3DSPR_SAMPLEMASK,
 };
 
 enum wined3d_data_type