diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 91653c140c..8547fc7e17 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -7435,6 +7435,12 @@ namespace ts {
                 type = <UnionType>createType(TypeFlags.Union | propagatedFlags);
                 unionTypes.set(id, type);
                 type.types = types;
+                /*
+                Note: This is the alias symbol (or lack thereof) that we see when we first encounter this union type.
+                For aliases of identical unions, eg `type T = A | B; type U = A | B`, the symbol of the first alias encountered is the aliasSymbol.
+                (In the language service, the order may depend on the order in which a user takes actions, such as hovering over symbols.)
+                It's important that we create equivalent union types only once, so that's an unfortunate side effect.
+                */
                 type.aliasSymbol = aliasSymbol;
                 type.aliasTypeArguments = aliasTypeArguments;
             }
@@ -7528,7 +7534,7 @@ namespace ts {
                 type = <IntersectionType>createType(TypeFlags.Intersection | propagatedFlags);
                 intersectionTypes.set(id, type);
                 type.types = typeSet;
-                type.aliasSymbol = aliasSymbol;
+                type.aliasSymbol = aliasSymbol; // See comment in `getUnionTypeFromSortedList`.
                 type.aliasTypeArguments = aliasTypeArguments;
             }
             return type;
diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index d2ac3dd0e7..87b4c8e930 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -245,7 +245,7 @@ namespace ts {
     const redForegroundEscapeSequence = "\u001b[91m";
     const yellowForegroundEscapeSequence = "\u001b[93m";
     const blueForegroundEscapeSequence = "\u001b[93m";
-    const gutterStyleSequence = "\u001b[100;30m";
+    const gutterStyleSequence = "\u001b[30;47m";
     const gutterSeparator = " ";
     const resetEscapeSequence = "\u001b[0m";
     const ellipsis = "...";
diff --git a/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt b/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt
index 7b7e3fea3e..9cac1423f3 100644
--- a/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt
+++ b/tests/baselines/reference/prettyContextNotDebugAssertion.errors.txt
@@ -1,6 +1,6 @@
 
-2 
-  
+2 
+  
 
 tests/cases/compiler/index.ts(2,1): error TS1005: '}' expected.