diff --git a/docs-master/Config.md b/docs-master/Config.md
index 1452694b7..3fb2ba655 100644
--- a/docs-master/Config.md
+++ b/docs-master/Config.md
@@ -198,8 +198,8 @@ gui:
       - blue
 
     # Background color of selected line when view doesn't have focus.
-    inactiveViewSelectedLineBgColor:
-      - bold
+    # Default: a suitable RGB grey computed from the terminal's background color.
+    inactiveViewSelectedLineBgColor: []
 
     # Foreground color of copied commit
     cherryPickedCommitFgColor:
diff --git a/pkg/config/theme_config.go b/pkg/config/theme_config.go
index 81554bf8e..04fdf3726 100644
--- a/pkg/config/theme_config.go
+++ b/pkg/config/theme_config.go
@@ -3,17 +3,61 @@ package config
 import (
 	"fmt"
 	"maps"
+	"math"
 	"reflect"
 	"slices"
+	"strconv"
 
+	"github.com/jesseduffield/lazygit/pkg/utils"
 	"github.com/samber/lo"
 )
 
 // ThemeForBackground returns gui.theme with the overrides for a dark or a light
-// background applied.
-func (c *GuiConfig) ThemeForBackground(lightBackground bool) ThemeConfig {
+// background applied, and with the defaults for that background in the fields
+// that neither of them sets. backgroundColor is the terminal's background color
+// as #rrggbb, or empty if we don't know it.
+func (c *GuiConfig) ThemeForBackground(lightBackground bool, backgroundColor string) ThemeConfig {
 	override := lo.Ternary(lightBackground, c.LightTheme, c.DarkTheme)
-	return mergeThemes(override, c.Theme)
+	return mergeThemes(override, c.Theme, themeDefaults(lightBackground, backgroundColor))
+}
+
+// themeDefaults returns the defaults of the theme fields whose default depends
+// on the terminal's background. GetDefaultConfig leaves these fields empty in
+// gui.theme, so that a value there comes from the user, and wins over these.
+//
+// They are derived from the background color, so that they keep the same
+// distance from it however dark or light it is. If we don't know the
+// background color, we assume black or white.
+func themeDefaults(lightBackground bool, backgroundColor string) ThemeConfig {
+	if len(backgroundColor) != 7 || !utils.IsValidHexValue(backgroundColor) {
+		backgroundColor = lo.Ternary(lightBackground, "#ffffff", "#000000")
+	}
+
+	if lightBackground {
+		return ThemeConfig{
+			InactiveViewSelectedLineBgColor: []string{mixHexColors(backgroundColor, "#000000", 0.15)},
+		}
+	}
+
+	return ThemeConfig{
+		InactiveViewSelectedLineBgColor: []string{mixHexColors(backgroundColor, "#ffffff", 0.3)},
+	}
+}
+
+// mixHexColors mixes two colors given as #rrggbb. amount is how much of b to
+// take: 0 gives a, 1 gives b.
+func mixHexColors(a, b string, amount float64) string {
+	channel := func(color string, i int) float64 {
+		value, _ := strconv.ParseUint(color[1+2*i:3+2*i], 16, 8)
+		return float64(value)
+	}
+
+	result := "#"
+	for i := range 3 {
+		mixed := channel(a, i) + (channel(b, i)-channel(a, i))*amount
+		result += fmt.Sprintf("%02x", int(math.Round(mixed)))
+	}
+	return result
 }
 
 // mergeThemes takes each field from the first of the themes that sets it. For
diff --git a/pkg/config/theme_config_test.go b/pkg/config/theme_config_test.go
index 1971a895b..a4bd39028 100644
--- a/pkg/config/theme_config_test.go
+++ b/pkg/config/theme_config_test.go
@@ -31,13 +31,13 @@ func TestThemeForBackground(t *testing.T) {
 		},
 	}
 
-	dark := gui.ThemeForBackground(false)
+	dark := gui.ThemeForBackground(false, "")
 	assert.Equal(t, []string{"yellow"}, dark.ActiveBorderColor)
 	assert.Equal(t, []string{"default"}, dark.InactiveBorderColor)
 	assert.Equal(t, map[string]string{"Alice": "red", "Bob": "blue"}, dark.AuthorColors)
 	assert.Equal(t, gui.Theme.BranchColorPatterns, dark.BranchColorPatterns)
 
-	light := gui.ThemeForBackground(true)
+	light := gui.ThemeForBackground(true, "")
 	assert.Equal(t, []string{"green"}, light.ActiveBorderColor)
 	assert.Equal(t, []string{"#777777"}, light.InactiveBorderColor)
 	assert.Equal(t, map[string]string{"Alice": "red", "Bob": "#000080"}, light.AuthorColors)
@@ -70,5 +70,54 @@ func TestEveryThemeFieldCanBeOverridden(t *testing.T) {
 
 	gui := GetDefaultConfig().Gui
 	gui.DarkTheme = override
-	assert.Equal(t, override, gui.ThemeForBackground(false))
+	assert.Equal(t, override, gui.ThemeForBackground(false, ""))
+}
+
+func TestThemeForBackgroundFallsBackToTheDefaultsForTheBackground(t *testing.T) {
+	gui := GetDefaultConfig().Gui
+	assert.Equal(t, []string{"#4d4d4d"}, gui.ThemeForBackground(false, "").InactiveViewSelectedLineBgColor)
+	assert.Equal(t, []string{"#d9d9d9"}, gui.ThemeForBackground(true, "").InactiveViewSelectedLineBgColor)
+
+	gui.Theme.InactiveViewSelectedLineBgColor = []string{"bold"}
+	assert.Equal(t, []string{"bold"}, gui.ThemeForBackground(false, "").InactiveViewSelectedLineBgColor)
+	assert.Equal(t, []string{"bold"}, gui.ThemeForBackground(true, "").InactiveViewSelectedLineBgColor)
+
+	gui.LightTheme.InactiveViewSelectedLineBgColor = []string{"white"}
+	assert.Equal(t, []string{"bold"}, gui.ThemeForBackground(false, "").InactiveViewSelectedLineBgColor)
+	assert.Equal(t, []string{"white"}, gui.ThemeForBackground(true, "").InactiveViewSelectedLineBgColor)
+}
+
+func TestBackgroundDefaultsAreDerivedFromTheBackgroundColor(t *testing.T) {
+	gui := GetDefaultConfig().Gui
+	assert.Equal(t, []string{"#626262"}, gui.ThemeForBackground(false, "#1e1e1e").InactiveViewSelectedLineBgColor)
+	assert.Equal(t, []string{"#d7d1c1"}, gui.ThemeForBackground(true, "#fdf6e3").InactiveViewSelectedLineBgColor)
+}
+
+// If gui.theme had a default for a field that also has a default for the
+// terminal's background, the former would always win.
+func TestFieldsWithBackgroundDefaultsHaveNoDefaultInGuiTheme(t *testing.T) {
+	genericDefaults := setThemeFields(GetDefaultConfig().Gui.Theme)
+	for _, field := range setThemeFields(themeDefaults(false, "")) {
+		assert.NotContains(t, genericDefaults, field)
+	}
+	for _, field := range setThemeFields(themeDefaults(true, "")) {
+		assert.NotContains(t, genericDefaults, field)
+	}
+}
+
+// If only one of the backgrounds had a default for a field, the field would
+// have no value at all with the other.
+func TestDarkAndLightDefaultsSetTheSameFields(t *testing.T) {
+	assert.Equal(t, setThemeFields(themeDefaults(false, "")), setThemeFields(themeDefaults(true, "")))
+}
+
+func setThemeFields(theme ThemeConfig) []string {
+	var fields []string
+	themeValue := reflect.ValueOf(theme)
+	for i := range themeValue.NumField() {
+		if themeValue.Field(i).Len() > 0 {
+			fields = append(fields, themeValue.Type().Field(i).Name)
+		}
+	}
+	return fields
 }
diff --git a/pkg/config/user_config.go b/pkg/config/user_config.go
index 01621f354..98a4a16c9 100644
--- a/pkg/config/user_config.go
+++ b/pkg/config/user_config.go
@@ -244,6 +244,7 @@ type ThemeConfig struct {
 	// See https://github.com/jesseduffield/lazygit/blob/master/docs/Config.md#highlighting-the-selected-line
 	SelectedLineBgColor []string `yaml:"selectedLineBgColor" jsonschema:"minItems=1,uniqueItems=true"`
 	// Background color of selected line when view doesn't have focus.
+	// Default: a suitable RGB grey computed from the terminal's background color.
 	InactiveViewSelectedLineBgColor []string `yaml:"inactiveViewSelectedLineBgColor" jsonschema:"minItems=1,uniqueItems=true"`
 	// Foreground color of copied commit
 	CherryPickedCommitFgColor []string `yaml:"cherryPickedCommitFgColor" jsonschema:"minItems=1,uniqueItems=true"`
@@ -890,18 +891,17 @@ func GetDefaultConfigForPlatform(platform string) *UserConfig {
 			ShortTimeFormat:          time.Kitchen,
 			ColorScheme:              "auto",
 			Theme: ThemeConfig{
-				ActiveBorderColor:               []string{"green", "bold"},
-				SearchingActiveBorderColor:      []string{"cyan", "bold"},
-				InactiveBorderColor:             []string{"default"},
-				OptionsTextColor:                []string{"blue"},
-				SelectedLineBgColor:             []string{"blue"},
-				InactiveViewSelectedLineBgColor: []string{"bold"},
-				CherryPickedCommitBgColor:       []string{"cyan"},
-				CherryPickedCommitFgColor:       []string{"blue"},
-				MarkedBaseCommitBgColor:         []string{"yellow"},
-				MarkedBaseCommitFgColor:         []string{"blue"},
-				UnstagedChangesColor:            []string{"red"},
-				DefaultFgColor:                  []string{"default"},
+				ActiveBorderColor:          []string{"green", "bold"},
+				SearchingActiveBorderColor: []string{"cyan", "bold"},
+				InactiveBorderColor:        []string{"default"},
+				OptionsTextColor:           []string{"blue"},
+				SelectedLineBgColor:        []string{"blue"},
+				CherryPickedCommitBgColor:  []string{"cyan"},
+				CherryPickedCommitFgColor:  []string{"blue"},
+				MarkedBaseCommitBgColor:    []string{"yellow"},
+				MarkedBaseCommitFgColor:    []string{"blue"},
+				UnstagedChangesColor:       []string{"red"},
+				DefaultFgColor:             []string{"default"},
 			},
 			CommitLength:                        CommitLengthConfig{Show: true},
 			SkipNoStagedFilesWarning:            false,
diff --git a/pkg/gui/gui.go b/pkg/gui/gui.go
index ebfc6d5f2..8d66e99b1 100644
--- a/pkg/gui/gui.go
+++ b/pkg/gui/gui.go
@@ -1252,7 +1252,7 @@ func (gui *Gui) showBreakingChangesMessage() {
 // applyTheme sets the colors of the app from the theme in the user config,
 // with the overrides for the terminal's background applied
 func (gui *Gui) applyTheme() {
-	themeConfig := gui.UserConfig().Gui.ThemeForBackground(gui.terminalHasLightBackground())
+	themeConfig := gui.UserConfig().Gui.ThemeForBackground(gui.terminalHasLightBackground(), gui.terminalBackgroundColor())
 	theme.UpdateTheme(themeConfig)
 	authors.SetCustomAuthors(themeConfig.AuthorColors)
 	presentation.SetCustomBranches(themeConfig.BranchColorPatterns)
@@ -1284,6 +1284,17 @@ func (gui *Gui) terminalHasLightBackground() bool {
 	}
 }
 
+// terminalBackgroundColor returns the background color that the terminal told
+// us, as #rrggbb. It returns "" if the terminal didn't tell us, or if
+// gui.colorScheme disagrees with it about whether the background is light.
+func (gui *Gui) terminalBackgroundColor() string {
+	detected := gui.g.DetectedColorScheme()
+	if (detected.ColorScheme == gocui.ColorSchemeLight) != gui.terminalHasLightBackground() {
+		return ""
+	}
+	return detected.Background
+}
+
 func (gui *Gui) onUIThread(f func() error) {
 	gui.g.Update(func(*gocui.Gui) error {
 		return f()
diff --git a/schema-master/config.json b/schema-master/config.json
index a00e6cc5b..00b398c17 100644
--- a/schema-master/config.json
+++ b/schema-master/config.json
@@ -786,10 +786,7 @@
               "type": "array",
               "minItems": 1,
               "uniqueItems": true,
-              "description": "Background color of selected line when view doesn't have focus.",
-              "default": [
-                "bold"
-              ]
+              "description": "Background color of selected line when view doesn't have focus.\nDefault: a suitable RGB grey computed from the terminal's background color."
             },
             "cherryPickedCommitFgColor": {
               "items": {
@@ -929,7 +926,7 @@
               "type": "array",
               "minItems": 1,
               "uniqueItems": true,
-              "description": "Background color of selected line when view doesn't have focus."
+              "description": "Background color of selected line when view doesn't have focus.\nDefault: a suitable RGB grey computed from the terminal's background color."
             },
             "cherryPickedCommitFgColor": {
               "items": {
@@ -1051,7 +1048,7 @@
               "type": "array",
               "minItems": 1,
               "uniqueItems": true,
-              "description": "Background color of selected line when view doesn't have focus."
+              "description": "Background color of selected line when view doesn't have focus.\nDefault: a suitable RGB grey computed from the terminal's background color."
             },
             "cherryPickedCommitFgColor": {
               "items": {