diff --git a/messages.go b/messages.go
index 01b799b2..e98197d0 100644
--- a/messages.go
+++ b/messages.go
@@ -24,7 +24,7 @@ type FieldDescription struct {
 	DataType        pgtype.OID
 	DataTypeSize    int16
 	DataTypeName    string
-	Modifier        uint32
+	Modifier        int32
 	FormatCode      int16
 }
 
diff --git a/pgmock/pgmock.go b/pgmock/pgmock.go
index fec0d3f6..4d15f7b8 100644
--- a/pgmock/pgmock.go
+++ b/pgmock/pgmock.go
@@ -229,7 +229,7 @@ where (
 					TableAttributeNumber: 65534,
 					DataTypeOID:          26,
 					DataTypeSize:         4,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 				{Name: "typname",
@@ -237,7 +237,7 @@ where (
 					TableAttributeNumber: 1,
 					DataTypeOID:          19,
 					DataTypeSize:         64,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 			},
@@ -455,7 +455,7 @@ where (
 					TableAttributeNumber: 65534,
 					DataTypeOID:          26,
 					DataTypeSize:         4,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 				{Name: "typname",
@@ -463,7 +463,7 @@ where (
 					TableAttributeNumber: 1,
 					DataTypeOID:          19,
 					DataTypeSize:         64,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 			},
@@ -496,7 +496,7 @@ where (
 					TableAttributeNumber: 65534,
 					DataTypeOID:          26,
 					DataTypeSize:         4,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 				{Name: "typname",
@@ -504,7 +504,7 @@ where (
 					TableAttributeNumber: 1,
 					DataTypeOID:          19,
 					DataTypeSize:         64,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 				{Name: "typbasetype",
@@ -512,7 +512,7 @@ where (
 					TableAttributeNumber: 65534,
 					DataTypeOID:          26,
 					DataTypeSize:         4,
-					TypeModifier:         4294967295,
+					TypeModifier:         -1,
 					Format:               0,
 				},
 			},
diff --git a/pgproto3/row_description.go b/pgproto3/row_description.go
index d0df11b0..3c5a6faa 100644
--- a/pgproto3/row_description.go
+++ b/pgproto3/row_description.go
@@ -19,7 +19,7 @@ type FieldDescription struct {
 	TableAttributeNumber uint16
 	DataTypeOID          uint32
 	DataTypeSize         int16
-	TypeModifier         uint32
+	TypeModifier         int32
 	Format               int16
 }
 
@@ -57,7 +57,7 @@ func (dst *RowDescription) Decode(src []byte) error {
 		fd.TableAttributeNumber = binary.BigEndian.Uint16(buf.Next(2))
 		fd.DataTypeOID = binary.BigEndian.Uint32(buf.Next(4))
 		fd.DataTypeSize = int16(binary.BigEndian.Uint16(buf.Next(2)))
-		fd.TypeModifier = binary.BigEndian.Uint32(buf.Next(4))
+		fd.TypeModifier = int32(binary.BigEndian.Uint32(buf.Next(4)))
 		fd.Format = int16(binary.BigEndian.Uint16(buf.Next(2)))
 
 		dst.Fields[i] = fd
@@ -80,7 +80,7 @@ func (src *RowDescription) Encode(dst []byte) []byte {
 		dst = pgio.AppendUint16(dst, fd.TableAttributeNumber)
 		dst = pgio.AppendUint32(dst, fd.DataTypeOID)
 		dst = pgio.AppendInt16(dst, fd.DataTypeSize)
-		dst = pgio.AppendUint32(dst, fd.TypeModifier)
+		dst = pgio.AppendInt32(dst, fd.TypeModifier)
 		dst = pgio.AppendInt16(dst, fd.Format)
 	}
 
diff --git a/stdlib/sql_test.go b/stdlib/sql_test.go
index 02b0655f..78f3e6d4 100644
--- a/stdlib/sql_test.go
+++ b/stdlib/sql_test.go
@@ -1030,7 +1030,7 @@ func TestConnQueryContextCancel(t *testing.T) {
 					Name:         "n",
 					DataTypeOID:  23,
 					DataTypeSize: 4,
-					TypeModifier: 4294967295,
+					TypeModifier: -1,
 				},
 			},
 		}),
@@ -1206,7 +1206,7 @@ func TestStmtQueryContextCancel(t *testing.T) {
 					Name:         "n",
 					DataTypeOID:  23,
 					DataTypeSize: 4,
-					TypeModifier: 4294967295,
+					TypeModifier: -1,
 				},
 			},
 		}),