diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 2bbf17e6098..c6473f2cb99 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -2432,12 +2432,14 @@ namespace ts {
             }
 
             // List of collected files is complete; validate exhautiveness if this is a project with a file list
-            if (options.composite && rootNames.length < files.length) {
-                const normalizedRootNames = rootNames.map(r => normalizePath(r).toLowerCase());
-                const sourceFiles = files.filter(f => !f.isDeclarationFile).map(f => normalizePath(f.path).toLowerCase());
-                for (const file of sourceFiles) {
-                    if (normalizedRootNames.every(r => r !== file)) {
-                        programDiagnostics.add(createCompilerDiagnostic(Diagnostics.File_0_is_not_in_project_file_list_Projects_must_list_all_files_or_use_an_include_pattern, file));
+            if (options.composite) {
+                const sourceFiles = files.filter(f => !f.isDeclarationFile);
+                if (rootNames.length < sourceFiles.length) {
+                    const normalizedRootNames = rootNames.map(r => normalizePath(r).toLowerCase());
+                    for (const file of sourceFiles.map(f => normalizePath(f.path).toLowerCase())) {
+                        if (normalizedRootNames.indexOf(file) === -1) {
+                            programDiagnostics.add(createCompilerDiagnostic(Diagnostics.File_0_is_not_in_project_file_list_Projects_must_list_all_files_or_use_an_include_pattern, file));
+                        }
                     }
                 }
             }