diff --git a/mk2rbc/mk2rbc.go b/mk2rbc/mk2rbc.go
index b9b7e2c..3ae8ab9 100644
--- a/mk2rbc/mk2rbc.go
+++ b/mk2rbc/mk2rbc.go
@@ -726,7 +726,7 @@
 func (ctx *parseContext) newDependentModule(path string, optional bool) *moduleInfo {
 	modulePath := ctx.loadedModulePath(path)
 	if mi, ok := ctx.dependentModules[modulePath]; ok {
-		mi.optional = mi.optional || optional
+		mi.optional = mi.optional && optional
 		return mi
 	}
 	moduleName := moduleNameForFile(path)
@@ -753,16 +753,21 @@
 
 	// In a simple case, the name of a module to inherit/include is known statically.
 	if path, ok := maybeString(pathExpr); ok {
+		// Note that even if this directive loads a module unconditionally, a module may be
+		// absent without causing any harm if this directive is inside an if/else block.
+		moduleShouldExist := loadAlways && ctx.ifNestLevel == 0
 		if strings.Contains(path, "*") {
 			if paths, err := fs.Glob(ctx.script.sourceFS, path); err == nil {
 				for _, p := range paths {
-					processModule(inheritedStaticModule{ctx.newDependentModule(p, !loadAlways), loadAlways})
+					mi := ctx.newDependentModule(p, !moduleShouldExist)
+					processModule(inheritedStaticModule{mi, loadAlways})
 				}
 			} else {
 				ctx.errorf(v, "cannot glob wildcard argument")
 			}
 		} else {
-			processModule(inheritedStaticModule{ctx.newDependentModule(path, !loadAlways), loadAlways})
+			mi := ctx.newDependentModule(path, !moduleShouldExist)
+			processModule(inheritedStaticModule{mi, loadAlways})
 		}
 		return
 	}
@@ -852,13 +857,13 @@
 
 func (ctx *parseContext) handleInheritModule(v mkparser.Node, pathExpr starlarkExpr, loadAlways bool) {
 	ctx.handleSubConfig(v, pathExpr, loadAlways, func(im inheritedModule) {
-		ctx.receiver.newNode(&inheritNode{im})
+		ctx.receiver.newNode(&inheritNode{im, loadAlways})
 	})
 }
 
 func (ctx *parseContext) handleInclude(v mkparser.Node, pathExpr starlarkExpr, loadAlways bool) {
 	ctx.handleSubConfig(v, pathExpr, loadAlways, func(im inheritedModule) {
-		ctx.receiver.newNode(&includeNode{im})
+		ctx.receiver.newNode(&includeNode{im, loadAlways})
 	})
 }