diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 86fbc2e6259..57207d0564a 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -800,12 +800,12 @@ namespace ts {
         }
 
         // Get source file from normalized fileName
-        function findSourceFile(fileName: string, normalizedAbsolutePath: Path, isDefaultLib: boolean, refFile?: SourceFile, refPos?: number, refEnd?: number): SourceFile {
-            if (filesByName.contains(normalizedAbsolutePath)) {
-                const file = filesByName.get(normalizedAbsolutePath);
+        function findSourceFile(fileName: string, path: Path, isDefaultLib: boolean, refFile?: SourceFile, refPos?: number, refEnd?: number): SourceFile {
+            if (filesByName.contains(path)) {
+                const file = filesByName.get(path);
                 // try to check if we've already seen this file but with a different casing in path
                 // NOTE: this only makes sense for case-insensitive file systems
-                if (file && options.forceConsistentCasingInFileNames && getNormalizedAbsolutePath(file.fileName, currentDirectory) !== normalizedAbsolutePath) {
+                if (file && options.forceConsistentCasingInFileNames && getNormalizedAbsolutePath(file.fileName, currentDirectory) !== getNormalizedAbsolutePath(fileName, currentDirectory)) {
                     reportFileNamesDifferOnlyInCasingError(fileName, file.fileName, refFile, refPos, refEnd);
                 }
 
@@ -823,18 +823,18 @@ namespace ts {
                 }
             });
 
-            filesByName.set(normalizedAbsolutePath, file);
+            filesByName.set(path, file);
             if (file) {
-                file.path = normalizedAbsolutePath;
+                file.path = path;
 
                 if (host.useCaseSensitiveFileNames()) {
                     // for case-sensitive file systems check if we've already seen some file with similar filename ignoring case
-                    const existingFile = filesByNameIgnoreCase.get(normalizedAbsolutePath);
+                    const existingFile = filesByNameIgnoreCase.get(path);
                     if (existingFile) {
                         reportFileNamesDifferOnlyInCasingError(fileName, existingFile.fileName, refFile, refPos, refEnd);
                     }
                     else {
-                        filesByNameIgnoreCase.set(normalizedAbsolutePath, file);
+                        filesByNameIgnoreCase.set(path, file);
                     }
                 }
 
diff --git a/tests/cases/unittests/moduleResolution.ts b/tests/cases/unittests/moduleResolution.ts
index c53cad5725a..9e316266bf6 100644
--- a/tests/cases/unittests/moduleResolution.ts
+++ b/tests/cases/unittests/moduleResolution.ts
@@ -354,6 +354,31 @@ export = C;
                 "moduleC.ts": "export var x"
             };
             test(files, { module: ts.ModuleKind.CommonJS, forceConsistentCasingInFileNames: true },  "", /* useCaseSensitiveFileNames */ false, ["moduleA.ts", "moduleB.ts", "moduleC.ts"], [1149, 1149]);
+        });
+
+        it("should fail when module names in 'require' calls has inconsistent casing and current directory has uppercase chars", () => {
+            const files: Map<string> = {
+                "/a/B/c/moduleA.ts": `import a = require("./ModuleC")`,
+                "/a/B/c/moduleB.ts": `import a = require("./moduleC")`,
+                "/a/B/c/moduleC.ts": "export var x",
+                "/a/B/c/moduleD.ts": `
+import a = require("./moduleA.ts");
+import b = require("./moduleB.ts");
+                `
+            };
+            test(files, { module: ts.ModuleKind.CommonJS, forceConsistentCasingInFileNames: true },  "/a/B/c", /* useCaseSensitiveFileNames */ false, ["moduleD.ts"], [1149]);
+        });
+        it("should not fail when module names in 'require' calls has consistent casing and current directory has uppercase chars", () => {
+            const files: Map<string> = {
+                "/a/B/c/moduleA.ts": `import a = require("./moduleC")`,
+                "/a/B/c/moduleB.ts": `import a = require("./moduleC")`,
+                "/a/B/c/moduleC.ts": "export var x",
+                "/a/B/c/moduleD.ts": `
+import a = require("./moduleA.ts");
+import b = require("./moduleB.ts");
+                `
+            };
+            test(files, { module: ts.ModuleKind.CommonJS, forceConsistentCasingInFileNames: true },  "/a/B/c", /* useCaseSensitiveFileNames */ false, ["moduleD.ts"], []);
         })
     });
 }
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