diff --git a/build/gobind-pinecone/monolith.go b/build/gobind-pinecone/monolith.go
index b51e97786..91bbb6873 100644
--- a/build/gobind-pinecone/monolith.go
+++ b/build/gobind-pinecone/monolith.go
@@ -218,6 +218,9 @@ func (m *DendriteMonolith) Start() {
 			if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 				panic("failed to load PEM key: " + err.Error())
 			}
+			if len(sk) != ed25519.PrivateKeySize {
+				panic("the private key is not long enough")
+			}
 		} else {
 			if sk, err = os.ReadFile(oldkeyfile); err != nil {
 				panic("failed to read the old private key: " + err.Error())
@@ -233,8 +236,13 @@ func (m *DendriteMonolith) Start() {
 		if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 			panic("failed to load PEM key: " + err.Error())
 		}
+		if len(sk) != ed25519.PrivateKeySize {
+			panic("the private key is not long enough")
+		}
 	}
 
+	pk = sk.Public().(ed25519.PublicKey)
+
 	var err error
 	m.listener, err = net.Listen("tcp", "localhost:65432")
 	if err != nil {
diff --git a/build/gobind-yggdrasil/monolith.go b/build/gobind-yggdrasil/monolith.go
index c671ae098..248b6c324 100644
--- a/build/gobind-yggdrasil/monolith.go
+++ b/build/gobind-yggdrasil/monolith.go
@@ -87,6 +87,9 @@ func (m *DendriteMonolith) Start() {
 			if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 				panic("failed to load PEM key: " + err.Error())
 			}
+			if len(sk) != ed25519.PrivateKeySize {
+				panic("the private key is not long enough")
+			}
 		} else {
 			if sk, err = os.ReadFile(oldkeyfile); err != nil {
 				panic("failed to read the old private key: " + err.Error())
@@ -103,8 +106,13 @@ func (m *DendriteMonolith) Start() {
 		if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 			panic("failed to load PEM key: " + err.Error())
 		}
+		if len(sk) != ed25519.PrivateKeySize {
+			panic("the private key is not long enough")
+		}
 	}
 
+	pk = sk.Public().(ed25519.PublicKey)
+
 	var err error
 	m.listener, err = net.Listen("tcp", "localhost:65432")
 	if err != nil {
diff --git a/cmd/dendrite-demo-pinecone/main.go b/cmd/dendrite-demo-pinecone/main.go
index 83b52132a..ff9cb5aa1 100644
--- a/cmd/dendrite-demo-pinecone/main.go
+++ b/cmd/dendrite-demo-pinecone/main.go
@@ -98,6 +98,9 @@ func main() {
 				if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 					panic("failed to load PEM key: " + err.Error())
 				}
+				if len(sk) != ed25519.PrivateKeySize {
+					panic("the private key is not long enough")
+				}
 			} else {
 				if sk, err = os.ReadFile(oldkeyfile); err != nil {
 					panic("failed to read the old private key: " + err.Error())
@@ -114,7 +117,13 @@ func main() {
 			if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 				panic("failed to load PEM key: " + err.Error())
 			}
+			if len(sk) != ed25519.PrivateKeySize {
+				panic("the private key is not long enough")
+			}
 		}
+
+		pk = sk.Public().(ed25519.PublicKey)
+
 		cfg.Defaults(config.DefaultOpts{
 			Generate:   true,
 			Monolithic: true,
@@ -136,7 +145,6 @@ func main() {
 		}
 	}
 
-	pk = sk.Public().(ed25519.PublicKey)
 	cfg.Global.ServerName = gomatrixserverlib.ServerName(hex.EncodeToString(pk))
 	cfg.Global.KeyID = gomatrixserverlib.KeyID(signing.KeyID)
 
diff --git a/cmd/dendrite-demo-yggdrasil/main.go b/cmd/dendrite-demo-yggdrasil/main.go
index 7445b6bfe..868d9826a 100644
--- a/cmd/dendrite-demo-yggdrasil/main.go
+++ b/cmd/dendrite-demo-yggdrasil/main.go
@@ -86,6 +86,9 @@ func main() {
 			if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 				panic("failed to load PEM key: " + err.Error())
 			}
+			if len(sk) != ed25519.PrivateKeySize {
+				panic("the private key is not long enough")
+			}
 		} else {
 			if sk, err = os.ReadFile(oldkeyfile); err != nil {
 				panic("failed to read the old private key: " + err.Error())
@@ -102,8 +105,13 @@ func main() {
 		if _, sk, err = config.LoadMatrixKey(keyfile, os.ReadFile); err != nil {
 			panic("failed to load PEM key: " + err.Error())
 		}
+		if len(sk) != ed25519.PrivateKeySize {
+			panic("the private key is not long enough")
+		}
 	}
 
+	pk = sk.Public().(ed25519.PublicKey)
+
 	// use custom config if config flag is set
 	if configFlagSet {
 		cfg = setup.ParseFlags(true)
@@ -129,7 +137,6 @@ func main() {
 		}
 	}
 
-	pk = sk.Public().(ed25519.PublicKey)
 	cfg.Global.ServerName = gomatrixserverlib.ServerName(hex.EncodeToString(pk))
 	cfg.Global.KeyID = gomatrixserverlib.KeyID(signing.KeyID)