diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 45be50b93a66e..cc911b946d444 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -3944,7 +3944,7 @@ namespace ts {
                 diagnostics = nonFileDiagnostics;
             }
 
-            insertSorted(diagnostics, diagnostic, compareDiagnostics);
+            insertSorted(diagnostics, diagnostic, compareDiagnosticsSkipRelatedInformation);
         }
 
         function getGlobalDiagnostics(): Diagnostic[] {
diff --git a/tests/baselines/reference/jsxSpreadOverwritesAttributeStrict.errors.txt b/tests/baselines/reference/jsxSpreadOverwritesAttributeStrict.errors.txt
index fefbc6cac4da0..9d751ce2216b4 100644
--- a/tests/baselines/reference/jsxSpreadOverwritesAttributeStrict.errors.txt
+++ b/tests/baselines/reference/jsxSpreadOverwritesAttributeStrict.errors.txt
@@ -6,13 +6,12 @@ tests/cases/conformance/jsx/file.tsx(20,23): error TS2783: 'b' is specified more
 tests/cases/conformance/jsx/file.tsx(21,17): error TS2783: 'a' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/jsx/file.tsx(21,23): error TS2783: 'd' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/jsx/file.tsx(22,17): error TS2783: 'a' is specified more than once, so this usage will be overwritten.
-tests/cases/conformance/jsx/file.tsx(22,17): error TS2783: 'a' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/jsx/file.tsx(22,23): error TS2783: 'd' is specified more than once, so this usage will be overwritten.
 
 
 !!! error TS2318: Cannot find global type 'CallableFunction'.
 !!! error TS2318: Cannot find global type 'NewableFunction'.
-==== tests/cases/conformance/jsx/file.tsx (8 errors) ====
+==== tests/cases/conformance/jsx/file.tsx (7 errors) ====
     import React = require('react');
     
     interface Props {
@@ -53,9 +52,6 @@ tests/cases/conformance/jsx/file.tsx(22,23): error TS2783: 'd' is specified more
                     ~~~~~
 !!! error TS2783: 'a' is specified more than once, so this usage will be overwritten.
 !!! related TS2785 tests/cases/conformance/jsx/file.tsx:22:29: This spread always overwrites this property.
-                    ~~~~~
-!!! error TS2783: 'a' is specified more than once, so this usage will be overwritten.
-!!! related TS2785 tests/cases/conformance/jsx/file.tsx:22:40: This spread always overwrites this property.
                           ~~~~~
 !!! error TS2783: 'd' is specified more than once, so this usage will be overwritten.
 !!! related TS2785 tests/cases/conformance/jsx/file.tsx:22:40: This spread always overwrites this property.
diff --git a/tests/baselines/reference/objectSpreadNegative.errors.txt b/tests/baselines/reference/objectSpreadNegative.errors.txt
index eeacad3ef0c98..df51023a99dd7 100644
--- a/tests/baselines/reference/objectSpreadNegative.errors.txt
+++ b/tests/baselines/reference/objectSpreadNegative.errors.txt
@@ -10,7 +10,6 @@ tests/cases/conformance/types/spread/objectSpreadNegative.ts(28,36): error TS111
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(28,53): error TS1117: An object literal cannot have multiple properties with the same name.
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(32,7): error TS2783: 'b' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(37,7): error TS2783: 'b' is specified more than once, so this usage will be overwritten.
-tests/cases/conformance/types/spread/objectSpreadNegative.ts(37,7): error TS2783: 'b' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(39,14): error TS2783: 'b' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(41,53): error TS2783: 'd' is specified more than once, so this usage will be overwritten.
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(43,7): error TS2783: 'a' is specified more than once, so this usage will be overwritten.
@@ -27,7 +26,7 @@ tests/cases/conformance/types/spread/objectSpreadNegative.ts(69,9): error TS2339
 tests/cases/conformance/types/spread/objectSpreadNegative.ts(74,11): error TS2339: Property 'a' does not exist on type '{}'.
 
 
-==== tests/cases/conformance/types/spread/objectSpreadNegative.ts (23 errors) ====
+==== tests/cases/conformance/types/spread/objectSpreadNegative.ts (22 errors) ====
     let o = { a: 1, b: 'no' }
     
     /// private propagates
@@ -91,9 +90,6 @@ tests/cases/conformance/types/spread/objectSpreadNegative.ts(74,11): error TS233
           ~~~~~~~
 !!! error TS2783: 'b' is specified more than once, so this usage will be overwritten.
 !!! related TS2785 tests/cases/conformance/types/spread/objectSpreadNegative.ts:37:16: This spread always overwrites this property.
-          ~~~~~~~
-!!! error TS2783: 'b' is specified more than once, so this usage will be overwritten.
-!!! related TS2785 tests/cases/conformance/types/spread/objectSpreadNegative.ts:37:23: This spread always overwrites this property.
     let combinedMid: { a: number, b: string, c: boolean } =
         { ...o3, b: 'ok', ...o4 }
                  ~~~~~~~
diff --git a/tests/cases/fourslash/deduplicateErrors.ts b/tests/cases/fourslash/deduplicateErrors.ts
new file mode 100644
index 0000000000000..a5ae588269650
--- /dev/null
+++ b/tests/cases/fourslash/deduplicateErrors.ts
@@ -0,0 +1,8 @@
+/// <reference path="./fourslash.ts" />
+
+////let lololol = 123;
+////
+////lololo/**/
+
+verify.encodedSemanticClassificationsLength("2020", 3);
+verify.numberOfErrorsInCurrentFile(1);
diff --git a/tests/cases/fourslash/insertReturnStatementInDuplicateIdentifierFunction.ts b/tests/cases/fourslash/insertReturnStatementInDuplicateIdentifierFunction.ts
index a131794c3f6f9..76e2db2fa008c 100644
--- a/tests/cases/fourslash/insertReturnStatementInDuplicateIdentifierFunction.ts
+++ b/tests/cases/fourslash/insertReturnStatementInDuplicateIdentifierFunction.ts
@@ -6,10 +6,10 @@
 goTo.marker();
 
 // Function with bodies can only merge with classes
-// Class declaration cannot implement overload list x 2
-verify.numberOfErrorsInCurrentFile(4);
+// Class declaration cannot implement overload list
+verify.numberOfErrorsInCurrentFile(2);
 
 // Shouldn't change the number of errors
 edit.insert('return null;');
-verify.numberOfErrorsInCurrentFile(4);
+verify.numberOfErrorsInCurrentFile(2);