diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 03cb84d715e..bc1ad956a16 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -8577,29 +8577,29 @@ namespace ts {
                 // and noise for experienced users. Here we can do an extra check in the error case to
                 // see whether or not substituting in the base types could simplify what we display to the user.
                 replaceLiterals: {
-                    let sourceReplacement;
-                    let targetReplacement;
+                    let sourceBase;
+                    let targetBase;
                     if (isTypeOfKind(source, TypeFlags.Literal)) {
-                        sourceReplacement = getBaseTypeOfLiteralType(source);
+                        sourceBase = getBaseTypeOfLiteralType(source);
                     }
                     if (isTypeOfKind(target, TypeFlags.Literal)) {
-                        targetReplacement = getBaseTypeOfLiteralType(target);
+                        targetBase = getBaseTypeOfLiteralType(target);
                     }
                     // If they both have the same base type, it's probably useful to report the literal type.
-                    if (sourceReplacement === targetReplacement) {
+                    if (sourceBase === targetBase) {
                         break replaceLiterals;
                     }
 
                     // We substitute the source with the base type *only* if
                     // the relation with the target remains the same.
-                    if (sourceReplacement && !isTypeRelatedTo(sourceReplacement, target, relation)) {
-                        source = sourceReplacement;
+                    if (sourceBase && !isTypeRelatedTo(sourceBase, target, relation)) {
+                        source = sourceBase;
                     }
 
                     // Likewise, only substitue the target if the relation with the source
                     // (or potentially the base-type of the source!) remains the same.
-                    if (targetReplacement && !isTypeRelatedTo(source, targetReplacement, relation)) {
-                        target = targetReplacement;
+                    if (targetBase && !isTypeRelatedTo(source, targetBase, relation)) {
+                        target = targetBase;
                     }
                 }