diff --git a/Source/Core/VideoCommon/BPMemory.h b/Source/Core/VideoCommon/BPMemory.h
index 5332c3e8d4..09f0efbaf7 100644
--- a/Source/Core/VideoCommon/BPMemory.h
+++ b/Source/Core/VideoCommon/BPMemory.h
@@ -531,16 +531,22 @@ struct FourTexUnits
 
 union GenMode
 {
-	struct
+	enum CullMode : u32
 	{
-		u32 numtexgens    : 4; //     0xF
-		u32 numcolchans   : 5; //   0x1E0
-		u32 multisampling : 1; //   0x200
-		u32 numtevstages  : 4; //  0x3C00
-		u32 cullmode      : 2; //  0xC000
-		u32 numindstages  : 3; // 0x30000
-		u32 zfreeze       : 5; //0x3C0000
+		CULL_NONE = 0,
+		CULL_BACK = 1, // cull back-facing primitives
+		CULL_FRONT = 2, // cull front-facing primitives
+		CULL_ALL = 3, // cull all primitives
 	};
+
+	BitField< 0,4,u32> numtexgens;
+	BitField< 4,5,u32> numcolchans;
+	BitField< 9,1,u32> multisampling;
+	BitField<10,4,u32> numtevstages;
+	BitField<14,2,CullMode> cullmode;
+	BitField<16,3,u32> numindstages;
+	BitField<19,5,u32> zfreeze;
+
 	u32 hex;
 };
 
diff --git a/Source/Core/VideoCommon/BPStructs.cpp b/Source/Core/VideoCommon/BPStructs.cpp
index 8b904a95f8..d3caaf49d3 100644
--- a/Source/Core/VideoCommon/BPStructs.cpp
+++ b/Source/Core/VideoCommon/BPStructs.cpp
@@ -91,9 +91,9 @@ void BPWritten(const BPCmd& bp)
 	case BPMEM_GENMODE: // Set the Generation Mode
 		{
 			PRIM_LOG("genmode: texgen=%d, col=%d, multisampling=%d, tev=%d, cullmode=%d, ind=%d, zfeeze=%d",
-			         bpmem.genMode.numtexgens, bpmem.genMode.numcolchans,
-			         bpmem.genMode.multisampling, bpmem.genMode.numtevstages+1, bpmem.genMode.cullmode,
-			         bpmem.genMode.numindstages, bpmem.genMode.zfreeze);
+			         (u32)bpmem.genMode.numtexgens, (u32)bpmem.genMode.numcolchans,
+			         (u32)bpmem.genMode.multisampling, (u32)bpmem.genMode.numtevstages+1, (u32)bpmem.genMode.cullmode,
+			         (u32)bpmem.genMode.numindstages, (u32)bpmem.genMode.zfreeze);
 
 			// Only call SetGenerationMode when cull mode changes.
 			if (bp.changes & 0xC000)