diff --git a/snes/fxpakpro/device.go b/snes/fxpakpro/device.go
index ba5401a..f899811 100644
--- a/snes/fxpakpro/device.go
+++ b/snes/fxpakpro/device.go
@@ -80,12 +80,15 @@ func (d *Device) MultiReadMemory(
 			Data:               make([]byte, read.Size),
 		}
 
-		mrsp[j].DeviceAddress = mapping.TranslateAddress(
+		mrsp[j].DeviceAddress, err = mapping.TranslateAddress(
 			read.RequestAddress,
 			read.RequestAddressSpace,
 			d.Mapping,
 			sni.AddressSpace_FxPakPro,
 		)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	// Break up larger reads (> 255 bytes) into 255-byte chunks:
@@ -219,12 +222,15 @@ func (d *Device) MultiWriteMemory(
 			Size:                len(write.Data),
 		}
 
-		mrsp[j].DeviceAddress = mapping.TranslateAddress(
+		mrsp[j].DeviceAddress, err = mapping.TranslateAddress(
 			write.RequestAddress,
 			write.RequestAddressSpace,
 			d.Mapping,
 			sni.AddressSpace_FxPakPro,
 		)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	// Break up larger writes (> 255 bytes) into 255-byte chunks:
diff --git a/snes/luabridge/memory.go b/snes/luabridge/memory.go
index f18803a..fcdb445 100644
--- a/snes/luabridge/memory.go
+++ b/snes/luabridge/memory.go
@@ -32,12 +32,16 @@ func (d *Device) MultiReadMemory(ctx context.Context, reads ...snes.MemoryReadRe
 
 	rsp = make([]snes.MemoryReadResponse, len(reads))
 	for j, read := range reads {
-		addr := mapping.TranslateAddress(
+		var addr uint32
+		addr, err = mapping.TranslateAddress(
 			read.RequestAddress,
 			read.RequestAddressSpace,
 			d.Mapping,
 			sni.AddressSpace_SnesABus,
 		)
+		if err != nil {
+			return
+		}
 
 		sb := bytes.NewBuffer(make([]byte, 0, 64))
 		_, _ = fmt.Fprintf(sb, "Read|%d|%d\n", addr, read.Size)
@@ -92,12 +96,16 @@ func (d *Device) MultiWriteMemory(ctx context.Context, writes ...snes.MemoryWrit
 
 	rsp = make([]snes.MemoryWriteResponse, len(writes))
 	for j, write := range writes {
-		addr := mapping.TranslateAddress(
+		var addr uint32
+		addr, err = mapping.TranslateAddress(
 			write.RequestAddress,
 			write.RequestAddressSpace,
 			d.Mapping,
 			sni.AddressSpace_SnesABus,
 		)
+		if err != nil {
+			return
+		}
 
 		// preallocate enough space to write the whole command:
 		sb := bytes.NewBuffer(make([]byte, 0, 24 + 4*len(write.Data)))
diff --git a/snes/mapping/translate.go b/snes/mapping/translate.go
index 6255422..de59183 100644
--- a/snes/mapping/translate.go
+++ b/snes/mapping/translate.go
@@ -1,53 +1,60 @@
 package mapping
 
 import (
+	"fmt"
 	"sni/protos/sni"
 	"sni/snes/mapping/exhirom"
 	"sni/snes/mapping/hirom"
 	"sni/snes/mapping/lorom"
 )
 
+var ErrUnknownMapping = fmt.Errorf("cannot map an address with an Unknown mapping; call MappingDetect or MappingSet first")
+
 func TranslateAddress(
 	address uint32,
 	space sni.AddressSpace,
 	mapping sni.MemoryMapping,
 	deviceSpace sni.AddressSpace,
-) uint32 {
+) (deviceAddress uint32, err error) {
 	switch space {
 	case sni.AddressSpace_Raw:
-		return address
+		return address, nil
 	case sni.AddressSpace_FxPakPro:
 		switch deviceSpace {
 		case sni.AddressSpace_Raw:
-			return address
+			return address, nil
 		case sni.AddressSpace_FxPakPro:
-			return address
+			return address, nil
 		case sni.AddressSpace_SnesABus:
 			switch mapping {
 			case sni.MemoryMapping_LoROM:
-				return lorom.PakAddressToBus(address)
+				return lorom.PakAddressToBus(address), nil
 			case sni.MemoryMapping_HiROM:
-				return hirom.PakAddressToBus(address)
+				return hirom.PakAddressToBus(address), nil
 			case sni.MemoryMapping_ExHiROM:
-				return exhirom.PakAddressToBus(address)
+				return exhirom.PakAddressToBus(address), nil
+			default:
+				return 0, ErrUnknownMapping
 			}
 		}
 	case sni.AddressSpace_SnesABus:
 		switch deviceSpace {
 		case sni.AddressSpace_Raw:
-			return address
+			return address, nil
 		case sni.AddressSpace_SnesABus:
-			return address
+			return address, nil
 		case sni.AddressSpace_FxPakPro:
 			switch mapping {
 			case sni.MemoryMapping_LoROM:
-				return lorom.BusAddressToPak(address)
+				return lorom.BusAddressToPak(address), nil
 			case sni.MemoryMapping_HiROM:
-				return hirom.BusAddressToPak(address)
+				return hirom.BusAddressToPak(address), nil
 			case sni.MemoryMapping_ExHiROM:
-				return exhirom.BusAddressToPak(address)
+				return exhirom.BusAddressToPak(address), nil
+			default:
+				return 0, ErrUnknownMapping
 			}
 		}
 	}
-	return address
+	return address, nil
 }
diff --git a/snes/retroarch/raclient.go b/snes/retroarch/raclient.go
index 9908d85..097f619 100644
--- a/snes/retroarch/raclient.go
+++ b/snes/retroarch/raclient.go
@@ -116,12 +116,15 @@ func (c *RAClient) MultiReadMemory(context context.Context, reads ...snes.Memory
 			Data:               make([]byte, 0, read.Size),
 		}
 
-		mrsp[j].DeviceAddress = mapping.TranslateAddress(
+		mrsp[j].DeviceAddress, err = mapping.TranslateAddress(
 			read.RequestAddress,
 			read.RequestAddressSpace,
 			c.Mapping,
 			sni.AddressSpace_SnesABus,
 		)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	// build multiple requests:
@@ -277,12 +280,15 @@ func (c *RAClient) MultiWriteMemory(context context.Context, writes ...snes.Memo
 			Size:                len(write.Data),
 		}
 
-		mrsps[i].DeviceAddress = mapping.TranslateAddress(
+		mrsps[i].DeviceAddress, err = mapping.TranslateAddress(
 			write.RequestAddress,
 			write.RequestAddressSpace,
 			c.Mapping,
 			sni.AddressSpace_SnesABus,
 		)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	for j, write := range writes {