diff --git a/server/handlers/sshd_config/analyzer/analyzer.go b/server/handlers/sshd_config/analyzer/analyzer.go
index 0007b09..72cb52e 100644
--- a/server/handlers/sshd_config/analyzer/analyzer.go
+++ b/server/handlers/sshd_config/analyzer/analyzer.go
@@ -54,6 +54,7 @@ func Analyze(
 		}
 	}
 
+	analyzeValuesAreValid(ctx)
 	analyzeMatchBlocks(ctx)
 	analyzeTokens(ctx)
 
diff --git a/server/handlers/sshd_config/analyzer/quotes.go b/server/handlers/sshd_config/analyzer/quotes.go
index a563bc5..e423510 100644
--- a/server/handlers/sshd_config/analyzer/quotes.go
+++ b/server/handlers/sshd_config/analyzer/quotes.go
@@ -11,12 +11,12 @@ import (
 func analyzeQuotesAreValid(
 	ctx *analyzerContext,
 ) {
-	for _, option := range ctx.document.Config.GetAllOptions() {
-		checkIsUsingDoubleQuotes(ctx, option.Key.Value, option.Key.LocationRange)
-		checkIsUsingDoubleQuotes(ctx, option.OptionValue.Value, option.OptionValue.LocationRange)
+	for _, info := range ctx.document.Config.GetAllOptions() {
+		checkIsUsingDoubleQuotes(ctx, info.Option.Key.Value, info.Option.Key.LocationRange)
+		checkIsUsingDoubleQuotes(ctx, info.Option.OptionValue.Value, info.Option.OptionValue.LocationRange)
 
-		checkQuotesAreClosed(ctx, option.Key.Value, option.Key.LocationRange)
-		checkQuotesAreClosed(ctx, option.OptionValue.Value, option.OptionValue.LocationRange)
+		checkQuotesAreClosed(ctx, info.Option.Key.Value, info.Option.Key.LocationRange)
+		checkQuotesAreClosed(ctx, info.Option.OptionValue.Value, info.Option.OptionValue.LocationRange)
 	}
 }
 
diff --git a/server/handlers/sshd_config/analyzer/tokens.go b/server/handlers/sshd_config/analyzer/tokens.go
index ee642db..4c29b2d 100644
--- a/server/handlers/sshd_config/analyzer/tokens.go
+++ b/server/handlers/sshd_config/analyzer/tokens.go
@@ -13,13 +13,13 @@ import (
 func analyzeTokens(
 	ctx *analyzerContext,
 ) {
-	for _, option := range ctx.document.Config.GetAllOptions() {
-		if option.Key == nil || option.OptionValue == nil {
+	for _, info := range ctx.document.Config.GetAllOptions() {
+		if info.Option.Key == nil || info.Option.OptionValue == nil {
 			continue
 		}
 
-		key := option.Key.Key
-		text := option.OptionValue.Value.Value
+		key := info.Option.Key.Key
+		text := info.Option.OptionValue.Value.Value
 		var tokens []string
 
 		if foundTokens, found := fields.OptionsTokensMap[key]; found {
@@ -39,7 +39,7 @@ func analyzeTokens(
 				}
 
 				ctx.diagnostics = append(ctx.diagnostics, protocol.Diagnostic{
-					Range:    option.OptionValue.ToLSPRange(),
+					Range:    info.Option.OptionValue.ToLSPRange(),
 					Message:  fmt.Sprintf("Token '%s' is not allowed for option '%s'", token, optionName),
 					Severity: &common.SeverityError,
 				})
diff --git a/server/handlers/sshd_config/analyzer/values.go b/server/handlers/sshd_config/analyzer/values.go
new file mode 100644
index 0000000..d29d8c7
--- /dev/null
+++ b/server/handlers/sshd_config/analyzer/values.go
@@ -0,0 +1,39 @@
+package analyzer
+
+import (
+	"config-lsp/handlers/sshd_config/diagnostics"
+	"config-lsp/handlers/sshd_config/fields"
+)
+
+func analyzeValuesAreValid(
+	ctx *analyzerContext,
+) {
+	// Check if there are unknown options
+	for _, info := range ctx.document.Config.GetAllOptions() {
+		normalizedName := fields.CreateNormalizedName(info.Option.Key.Value.Value)
+
+		var isUnknown bool = true
+
+		// Check if the option is unknown
+		if info.MatchBlock == nil {
+			// All options are allowed
+			if _, found := fields.Options[normalizedName]; found {
+				isUnknown = false
+			}
+		} else {
+			// Only `MatchAllowedOptions` are allowed
+			if _, found := fields.MatchAllowedOptions[normalizedName]; found {
+				isUnknown = false
+			}
+		}
+
+		if isUnknown {
+			ctx.diagnostics = append(ctx.diagnostics, diagnostics.GenerateUnknownOption(
+				info.Option.Key.ToLSPRange(),
+				info.Option.Key.Value.Value,
+			))
+
+			ctx.document.Indexes.UnknownOptions[info.Option.Start.Line] = info
+		}
+	}
+}
diff --git a/server/handlers/sshd_config/analyzer/values_test.go b/server/handlers/sshd_config/analyzer/values_test.go
new file mode 100644
index 0000000..b09df8c
--- /dev/null
+++ b/server/handlers/sshd_config/analyzer/values_test.go
@@ -0,0 +1,34 @@
+package analyzer
+
+import (
+	testutils_test "config-lsp/handlers/sshd_config/test_utils"
+	"testing"
+
+	protocol "github.com/tliron/glsp/protocol_3_16"
+)
+
+func TestUnknownOptionExample(
+	t *testing.T,
+) {
+	d := testutils_test.DocumentFromInput(t, `
+ThisOptionDoesNotExist okay
+`)
+	ctx := &analyzerContext{
+		document:    d,
+		diagnostics: make([]protocol.Diagnostic, 0),
+	}
+
+	analyzeValuesAreValid(ctx)
+
+	if !(len(ctx.diagnostics) == 1) {
+		t.Errorf("Expected 1 error, got %v", len(ctx.diagnostics))
+	}
+
+	if !(len(ctx.document.Indexes.UnknownOptions) == 1) {
+		t.Errorf("Expected 1 unknown option, got %v", len(ctx.document.Indexes.UnknownOptions))
+	}
+
+	if !(ctx.document.Indexes.UnknownOptions[0].Option.Key.Value.Value == "ThisOptionDoesNotExist") {
+		t.Errorf("Expected 'ThisOptionDoesNotExist', got %v", ctx.document.Indexes.UnknownOptions[0].Option.Key.Value.Value)
+	}
+}
diff --git a/server/handlers/sshd_config/ast/sshd_config_ast_utils.go b/server/handlers/sshd_config/ast/sshd_config_ast_utils.go
new file mode 100644
index 0000000..aeebea8
--- /dev/null
+++ b/server/handlers/sshd_config/ast/sshd_config_ast_utils.go
@@ -0,0 +1,8 @@
+// Contains structs that are used as utilities, but are
+// not used for the AST itself
+package ast
+
+type SSHDOptionInfo struct {
+	MatchBlock *SSHDMatchBlock
+	Option     *SSHDOption
+}
diff --git a/server/handlers/sshd_config/ast/sshd_config_fields.go b/server/handlers/sshd_config/ast/sshd_config_fields.go
index 11546d4..c5960fc 100644
--- a/server/handlers/sshd_config/ast/sshd_config_fields.go
+++ b/server/handlers/sshd_config/ast/sshd_config_fields.go
@@ -64,26 +64,32 @@ func (c SSHDConfig) FindOption(line uint32) (*SSHDOption, *SSHDMatchBlock) {
 	return nil, nil
 }
 
-func (c SSHDConfig) GetAllOptions() []*SSHDOption {
-	options := make(
-		[]*SSHDOption,
+func (c SSHDConfig) GetAllOptions() []SSHDOptionInfo {
+	infos := make(
+		[]SSHDOptionInfo,
 		0,
 		// Approximation, this does not need to be exact
 		c.Options.Size()+10,
 	)
 
+	var currentMatchBlock *SSHDMatchBlock = nil
+
 	for _, rawEntry := range c.Options.Values() {
 		switch entry := rawEntry.(type) {
 		case *SSHDOption:
-			options = append(options, entry)
+			infos = append(infos, SSHDOptionInfo{
+				Option:     entry,
+				MatchBlock: currentMatchBlock,
+			})
 		case *SSHDMatchBlock:
-			options = append(options, entry.MatchOption)
+			currentMatchBlock = entry
 
-			for _, rawOption := range entry.Options.Values() {
-				options = append(options, rawOption.(*SSHDOption))
-			}
+			infos = append(infos, SSHDOptionInfo{
+				Option:     entry.MatchOption,
+				MatchBlock: currentMatchBlock,
+			})
 		}
 	}
 
-	return options
+	return infos
 }
diff --git a/server/handlers/sshd_config/diagnostics/diagnostics.go b/server/handlers/sshd_config/diagnostics/diagnostics.go
new file mode 100644
index 0000000..86b96f0
--- /dev/null
+++ b/server/handlers/sshd_config/diagnostics/diagnostics.go
@@ -0,0 +1,19 @@
+package diagnostics
+
+import (
+	"config-lsp/common"
+	"fmt"
+
+	protocol "github.com/tliron/glsp/protocol_3_16"
+)
+
+func GenerateUnknownOption(
+	diagnosticRange protocol.Range,
+	optionName string,
+) protocol.Diagnostic {
+	return protocol.Diagnostic{
+		Range:    diagnosticRange,
+		Message:  fmt.Sprintf("Unknown option: %s", optionName),
+		Severity: &common.SeverityError,
+	}
+}
diff --git a/server/handlers/sshd_config/indexes/indexes.go b/server/handlers/sshd_config/indexes/indexes.go
index 236b359..656f36d 100644
--- a/server/handlers/sshd_config/indexes/indexes.go
+++ b/server/handlers/sshd_config/indexes/indexes.go
@@ -37,4 +37,6 @@ type SSHDIndexes struct {
 	AllOptionsPerName map[fields.NormalizedOptionName](map[*ast.SSHDMatchBlock]([]*ast.SSHDOption))
 
 	Includes map[uint32]*SSHDIndexIncludeLine
+
+	UnknownOptions map[uint32]ast.SSHDOptionInfo
 }
diff --git a/server/handlers/sshd_config/indexes/indexes_handlers.go b/server/handlers/sshd_config/indexes/indexes_handlers.go
index 5c90047..76d2cfb 100644
--- a/server/handlers/sshd_config/indexes/indexes_handlers.go
+++ b/server/handlers/sshd_config/indexes/indexes_handlers.go
@@ -18,6 +18,7 @@ func CreateIndexes(config ast.SSHDConfig) (*SSHDIndexes, []common.LSPError) {
 	indexes := &SSHDIndexes{
 		AllOptionsPerName: make(map[fields.NormalizedOptionName](map[*ast.SSHDMatchBlock]([]*ast.SSHDOption))),
 		Includes:          make(map[uint32]*SSHDIndexIncludeLine),
+		UnknownOptions:    make(map[uint32]ast.SSHDOptionInfo),
 	}
 
 	it := config.Options.Iterator()