diff --git a/accounts/abi/error_handling.go b/accounts/abi/error_handling.go
index c106e9ac43..9ef96c571b 100644
--- a/accounts/abi/error_handling.go
+++ b/accounts/abi/error_handling.go
@@ -23,15 +23,16 @@ import (
 )
 
 var (
-	errBadBool   = errors.New("abi: improperly encoded boolean value")
-	errBadUint8  = errors.New("abi: improperly encoded uint8 value")
-	errBadUint16 = errors.New("abi: improperly encoded uint16 value")
-	errBadUint32 = errors.New("abi: improperly encoded uint32 value")
-	errBadUint64 = errors.New("abi: improperly encoded uint64 value")
-	errBadInt8   = errors.New("abi: improperly encoded int8 value")
-	errBadInt16  = errors.New("abi: improperly encoded int16 value")
-	errBadInt32  = errors.New("abi: improperly encoded int32 value")
-	errBadInt64  = errors.New("abi: improperly encoded int64 value")
+	errBadBool     = errors.New("abi: improperly encoded boolean value")
+	errBadUint8    = errors.New("abi: improperly encoded uint8 value")
+	errBadUint16   = errors.New("abi: improperly encoded uint16 value")
+	errBadUint32   = errors.New("abi: improperly encoded uint32 value")
+	errBadUint64   = errors.New("abi: improperly encoded uint64 value")
+	errBadInt8     = errors.New("abi: improperly encoded int8 value")
+	errBadInt16    = errors.New("abi: improperly encoded int16 value")
+	errBadInt32    = errors.New("abi: improperly encoded int32 value")
+	errBadInt64    = errors.New("abi: improperly encoded int64 value")
+	errInvalidSign = errors.New("abi: negatively-signed value cannot be packed into uint parameter")
 )
 
 // formatSliceString formats the reflection kind with the given slice size
diff --git a/accounts/abi/pack.go b/accounts/abi/pack.go
index 35590df1dd..78c2b87cbf 100644
--- a/accounts/abi/pack.go
+++ b/accounts/abi/pack.go
@@ -39,7 +39,7 @@ func validateNum(t Type, reflectValue reflect.Value) error {
 	if t.T == UintTy && reflectValue.Kind() == reflect.Ptr {
 		val := new(big.Int).Set(reflectValue.Interface().(*big.Int))
 		if val.Sign() == -1 {
-			return fmt.Errorf("cannot pack negative big.Int value to a uint type")
+			return errInvalidSign
 		}
 	}
 	return nil
diff --git a/accounts/abi/unpack_test.go b/accounts/abi/unpack_test.go
index 74db298b3f..90713c03ca 100644
--- a/accounts/abi/unpack_test.go
+++ b/accounts/abi/unpack_test.go
@@ -1014,128 +1014,134 @@ func TestPackAndUnpackIncompatibleNumber(t *testing.T) {
 	cases := []struct {
 		decodeType  string
 		inputValue  *big.Int
-		err         error
+		unpackErr   error
+		packErr     error
 		expectValue interface{}
 	}{
 		{
 			decodeType: "uint8",
 			inputValue: big.NewInt(math.MaxUint8 + 1),
-			err:        errBadUint8,
+			unpackErr:  errBadUint8,
 		},
 		{
 			decodeType:  "uint8",
 			inputValue:  big.NewInt(math.MaxUint8),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: uint8(math.MaxUint8),
 		},
 		{
 			decodeType: "uint16",
 			inputValue: big.NewInt(math.MaxUint16 + 1),
-			err:        errBadUint16,
+			unpackErr:  errBadUint16,
 		},
 		{
 			decodeType:  "uint16",
 			inputValue:  big.NewInt(math.MaxUint16),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: uint16(math.MaxUint16),
 		},
 		{
 			decodeType: "uint32",
 			inputValue: big.NewInt(math.MaxUint32 + 1),
-			err:        errBadUint32,
+			unpackErr:  errBadUint32,
 		},
 		{
 			decodeType:  "uint32",
 			inputValue:  big.NewInt(math.MaxUint32),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: uint32(math.MaxUint32),
 		},
 		{
 			decodeType: "uint64",
 			inputValue: maxU64Plus1,
-			err:        errBadUint64,
+			unpackErr:  errBadUint64,
 		},
 		{
 			decodeType:  "uint64",
 			inputValue:  maxU64,
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: uint64(math.MaxUint64),
 		},
 		{
 			decodeType:  "uint256",
 			inputValue:  maxU64Plus1,
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: maxU64Plus1,
 		},
 		{
 			decodeType: "int8",
 			inputValue: big.NewInt(math.MaxInt8 + 1),
-			err:        errBadInt8,
+			unpackErr:  errBadInt8,
 		},
 		{
-			decodeType: "int8",
 			inputValue: big.NewInt(math.MinInt8 - 1),
-			err:        errBadInt8,
+			packErr:    errInvalidSign,
 		},
 		{
 			decodeType:  "int8",
 			inputValue:  big.NewInt(math.MaxInt8),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: int8(math.MaxInt8),
 		},
 		{
 			decodeType: "int16",
 			inputValue: big.NewInt(math.MaxInt16 + 1),
-			err:        errBadInt16,
+			unpackErr:  errBadInt16,
 		},
 		{
-			decodeType: "int16",
 			inputValue: big.NewInt(math.MinInt16 - 1),
-			err:        errBadInt16,
+			packErr:    errInvalidSign,
 		},
 		{
 			decodeType:  "int16",
 			inputValue:  big.NewInt(math.MaxInt16),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: int16(math.MaxInt16),
 		},
 		{
 			decodeType: "int32",
 			inputValue: big.NewInt(math.MaxInt32 + 1),
-			err:        errBadInt32,
+			unpackErr:  errBadInt32,
 		},
 		{
-			decodeType: "int32",
 			inputValue: big.NewInt(math.MinInt32 - 1),
-			err:        errBadInt32,
+			packErr:    errInvalidSign,
 		},
 		{
 			decodeType:  "int32",
 			inputValue:  big.NewInt(math.MaxInt32),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: int32(math.MaxInt32),
 		},
 		{
 			decodeType: "int64",
 			inputValue: new(big.Int).Add(big.NewInt(math.MaxInt64), big.NewInt(1)),
-			err:        errBadInt64,
+			unpackErr:  errBadInt64,
 		},
 		{
-			decodeType: "int64",
 			inputValue: new(big.Int).Sub(big.NewInt(math.MinInt64), big.NewInt(1)),
-			err:        errBadInt64,
+			packErr:    errInvalidSign,
 		},
 		{
 			decodeType:  "int64",
 			inputValue:  big.NewInt(math.MaxInt64),
-			err:         nil,
+			unpackErr:   nil,
 			expectValue: int64(math.MaxInt64),
 		},
 	}
 	for i, testCase := range cases {
 		packed, err := encodeABI.Pack(testCase.inputValue)
-		if err != nil {
-			panic(err)
+		if testCase.packErr != nil {
+			if err == nil {
+				t.Fatalf("expected packing of testcase input value to fail")
+			}
+			if err != testCase.packErr {
+				t.Fatalf("expected error '%v', got '%v'", testCase.packErr, err)
+			}
+			continue
+		}
+		if err != nil && err != testCase.packErr {
+			panic(fmt.Errorf("unexpected error packing test-case input: %v", err))
 		}
 		ty, err := NewType(testCase.decodeType, "", nil)
 		if err != nil {
@@ -1145,8 +1151,8 @@ func TestPackAndUnpackIncompatibleNumber(t *testing.T) {
 			{Type: ty},
 		}
 		decoded, err := decodeABI.Unpack(packed)
-		if err != testCase.err {
-			t.Fatalf("Expected error %v, actual error %v. case %d", testCase.err, err, i)
+		if err != testCase.unpackErr {
+			t.Fatalf("Expected error %v, actual error %v. case %d", testCase.unpackErr, err, i)
 		}
 		if err != nil {
 			continue