diff --git a/cmd/geth/genesis_test.go b/cmd/geth/genesis_test.go
new file mode 100644
index 0000000000000000000000000000000000000000..7485d7d89ebecd697e79ae471f66e6a19d69c7c3
--- /dev/null
+++ b/cmd/geth/genesis_test.go
@@ -0,0 +1,105 @@
+// Copyright 2016 The go-ethereum Authors
+// This file is part of go-ethereum.
+//
+// go-ethereum is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// go-ethereum is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with go-ethereum. If not, see <http://www.gnu.org/licenses/>.
+
+package main
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+)
+
+var customGenesisTests = []struct {
+	genesis string
+	query   string
+	result  string
+}{
+	// Plain genesis file without anything extra
+	{
+		genesis: `{
+			"alloc"      : {},
+			"coinbase"   : "0x0000000000000000000000000000000000000000",
+			"difficulty" : "0x20000",
+			"extraData"  : "",
+			"gasLimit"   : "0x2fefd8",
+			"nonce"      : "0x0000000000000042",
+			"mixhash"    : "0x0000000000000000000000000000000000000000000000000000000000000000",
+			"parentHash" : "0x0000000000000000000000000000000000000000000000000000000000000000",
+			"timestamp"  : "0x00"
+		}`,
+		query:  "eth.getBlock(0).nonce",
+		result: "0x0000000000000042",
+	},
+	// Genesis file with an empty chain configuration (ensure missing fields work)
+	{
+		genesis: `{
+			"alloc"      : {},
+			"coinbase"   : "0x0000000000000000000000000000000000000000",
+			"difficulty" : "0x20000",
+			"extraData"  : "",
+			"gasLimit"   : "0x2fefd8",
+			"nonce"      : "0x0000000000000042",
+			"mixhash"    : "0x0000000000000000000000000000000000000000000000000000000000000000",
+			"parentHash" : "0x0000000000000000000000000000000000000000000000000000000000000000",
+			"timestamp"  : "0x00",
+			"config"     : {}
+		}`,
+		query:  "eth.getBlock(0).nonce",
+		result: "0x0000000000000042",
+	},
+	// Genesis file with specific chain configurations
+	{
+		genesis: `{
+			"alloc"      : {},
+			"coinbase"   : "0x0000000000000000000000000000000000000000",
+			"difficulty" : "0x20000",
+			"extraData"  : "",
+			"gasLimit"   : "0x2fefd8",
+			"nonce"      : "0x0000000000000042",
+			"mixhash"    : "0x0000000000000000000000000000000000000000000000000000000000000000",
+			"parentHash" : "0x0000000000000000000000000000000000000000000000000000000000000000",
+			"timestamp"  : "0x00",
+			"config"     : {
+				"homesteadBlock" : 314,
+			},
+		}`,
+		query:  "eth.getBlock(0).nonce",
+		result: "0x0000000000000042",
+	},
+}
+
+// Tests that initializing Geth with a custom genesis block and chain definitions
+// work properly.
+func TestCustomGenesis(t *testing.T) {
+	for i, tt := range customGenesisTests {
+		// Create a temporary data directory to use and inspect later
+		datadir := tmpdir(t)
+		defer os.RemoveAll(datadir)
+
+		// Initialize the data directory with the custom genesis block
+		json := filepath.Join(datadir, "genesis.json")
+		if err := ioutil.WriteFile(json, []byte(tt.genesis), 0600); err != nil {
+			t.Fatalf("test %d: failed to write genesis file: %v", i, err)
+		}
+		runGeth(t, "--datadir", datadir, "init", json).cmd.Wait()
+
+		// Query the custom genesis block
+		geth := runGeth(t, "--datadir", datadir, "--maxpeers", "0", "--nodiscover", "--nat", "none", "--ipcdisable", "--exec", tt.query, "console")
+		geth.expectRegexp(tt.result)
+		geth.expectExit()
+	}
+}
diff --git a/core/config.go b/core/config.go
index d557ae5a4d54dbd187c511753a5e489303cf8dc8..d04b00e9c345ca7b867e5f428fa1d52033b4cddc 100644
--- a/core/config.go
+++ b/core/config.go
@@ -39,7 +39,7 @@ type ChainConfig struct {
 
 // IsHomestead returns whether num is either equal to the homestead block or greater.
 func (c *ChainConfig) IsHomestead(num *big.Int) bool {
-	if num == nil {
+	if c.HomesteadBlock == nil || num == nil {
 		return false
 	}
 	return num.Cmp(c.HomesteadBlock) >= 0